Packaging Materials — Second Edition ian Toss and Ron Goddard Publited by Pira International Randalls Road Lemberhesd Surrey Ketz2 7RU ‘+44 (0) 1372 202080 Foe: tad (0) 1372 602079 E-mail publications @pir.couk lnepilirrpeacauk!“The facts set out in thie publication are fom sources wich we Sieve tobe veliable, Hower, we accept no legal ibility of ary ind forthe publication contents, nor fr the information con- fained therein, nor conclusions dram by any party from [No part of thi publication may be seproduced, stored in ¢ Tetreval system, or traamitted in any fore or by any means, eetonie, mechanical, photocopying, recording or otherwise, ‘vihout the prior permission of the Copytght owner (© Copytgt Pies International 1998 ISDN 1 85802 2622 Repent 2004 “Typeset inthe UK by Lewis Marshal, Epsom, Suey Prine and bound in the UK by TH Dig, Past, Comal Contents List of figures se of abies Pent Factors luencing material selection Chapter The selection and use of packaging materials Sursteie 0 reduce and conseve Exeraal factorsinfuencing the choice of mnterals RRequiremens for selection of packaging ‘aaterile ‘Bdnotes for Pare 1 Past? Survey of raditfonal materials Chanter 2 Wood and paper-based materials Peper Paperboard (Corzugated fibreboard Corie Chapter 3. Glass Lightweight ane stent [New developments Chapter 4. Metals Cans ‘Alin fil and tape Stel drums and pail Endnotes for Pat 2ae oe Pachaging Materials Pert3 Synthetic materials CCoapter5 Introduction to plasties Piastcs processing Recycling Chapter 6 Polyolefins — polyethylene and polypropylene Pelyetplene (FE) Polypropyiene (PP) Chapter 7 Vinyl-based polymers Polyvinyl chloride (PVC) Polyvinylidene chocide (PVAC) Polyvinyl alcotol (PVOH), ethylene vinyl aleshot (GEVOH) and etiylene vinyl acre (EVA) ‘Chapter 8 Styrente plastics Polystyrene PS) ‘Siyrene copalymers — ABS, SAN and SB Chapter 9 Polyesters Polyesyleneerephthalate (PET) ‘Chapter 10Nslon (polyamide) ‘Nylon fin ‘Chapter 11 Cellophane regenerated cellulose film) Cellulose acetate (Chapter 12 Plastics’ barrier properties and. performance ‘Barrier property comparison (Other high bacrier plastics — HPs and ‘Buoropotymne ‘Mechanical strength comparison (Other high peeformence plastics Endnotes fr part 3 ‘ 4 82 85 86 95 ror 101 105 108 a rn na ur 47 w 8 131 Bs 135 wr 139 m1 146 Conn, - Part'd Composite and ancillary materials “Chapter 13 Fextbles and other composite materials [Laminates and ebexcrasions Surface costings and treatments Plastics eda Plastic bleads and alloys Paperboard ad metal composie structures (Chapter 1¢ Amellary materials ‘Endnotes for Pare 4 Pew Conclusions and references (Chapter 15 Material comparisons and conclusions ‘Maker assesmene of mat ‘Technic! performance of materials Tnvronmental profiles of materials Conetosion Chapter 16 Packaging materials brary ‘General packaging technology Darel: Material seleeton factors Part 2 Tradiional packaging mates Par 3: Plastic packaging materials ‘Pat 4: Composites and ancillary materials Index 151 154 158 165 168 169 13 13 116 m 19 184 189 93 194 197 199 202 205 205 206 208 210 aus 207List of tables 1 13 14 15 16 a 12 123 13a ‘Major world packaging supplies, 1994 ‘Werld packaging production by value 3 tonnage, 1995 ‘Raw material cosas a percentage of, container cost (in general) Peclaging material recycling retes inthe USA Dekaging materials and thle forms Decorating options for various packaging materials World packaging paper and bosed production, 1993-98 ‘Main packasing papers ‘Commen forms ofeorrugnted fibreboard ‘World plastics apparent consumption, 1994-2000 (milion tons, rounded) Polymer types used in packaging, ‘rope only, 1889-95. Type empersture ranges at which a plas tan be het sesled Relative densities of polethyenes US packaging markets for HDPE, 1997 US packaging meskes for conventional LDPE fins, 1997 US packaging maskets foe LLDPE fms, 1997 US packaging markes for PP, 1997 US packaging markets for PVC, 1997 [EVOH structares and applications ‘US packaging markets for PS, 1997 US packaging markets fr PET, 1997 ‘Wate: vapour capsmision rates of elected polymers ‘onygen permeability of selected polymers “Type plastic mechanical properties Polymerfim demand fr flexible packaging in western Burope: forecast, 1995-2001 (000 toanes) 32 39 2 87 90 oo 93 7 102 08 us 136 136 140pe it 7 15a 152 153 Package Motil: “Marker profile performance asessment “Technical performance asessment vironmencal performance asessment 194 Lot 200 List of figures m1 134 132 Regular slotted container (Corrugated forebourdstuctaret Double seam “Typical excruder ‘Typieal im blowing equipment Succ blow moulding Injection moulding ‘Thermoforming SPT resin coding system Repeat unt of polyethylene High, low and liner low density polyethylene Thotati and atic polypropylene Repeat units of polyethylene and PVC Coererssion Layout of vacuum metalizer 38 a 58 5 7 80 al a1 83 85 88 36 101 156 161Part 1 Factors influencing material selection Tee ee eeavroeto cre 1 The selection and use of packaging materials Packaging is big business Throughout the world large quantities of material are used for the production of packeging. One est- ‘ate, from the Woeld Packaging Organization, valves material usage alone tobe over 1350 milion tons, with a estimated annual value of over USSTS billion! Jn addition to the materials used, lange amounts of other resources are employed in the extraction, pureation and pro- cesing of packaging materials, Significant quantities of energy, ‘osily inthe form of fss fuel, reused, Resources are requied for the filing, closing and dspotl of packages. Packaging alto facilitates the movement of other material in business, commerce and tade. Every product, om food and consumer products to building materials and auto part, is hipped or sold in package. Many products require the we ofa series of packages ducing their wansformation from raw mateils to finished goods. {A culture's packaging needs are slated co ite resources, demo- sgeaphics and technology “The spread of packaging consumption shown in Table 11 refers the degree of sfuence and innovation in the mose developed ‘countries ofthe USA, Busope and Asa, These are the thee main consuming regions inthe World, although consumption i ether ‘countries inreasng with development. Packaging is en international activity and the exchange oftchai- cal information has never been better. Ie doesnot take long forGor Packasng Padang Ussuillon production production eo Essriion 1 oe weezer 1 2 oan ut a 3 3 Gamay = aes ast a & Fame’ thes ieaas 3 5 oy joa issi8 ir 6 tk Woe aie 3 ‘Seuss Horn Wid aap Bas Ps eenconl GO} pa ny significant development in one part of the world to become oun to interested peaciioners inal thes, ln view ofthe viel role of peckaping i improving the quality of life and reducing the losses of food end other products in developing countries, such {nteratonal xpoitason of improved technology i este "There are four basic packaging materials: las metal; pas and wood-based materials (including paper and paperboard, ‘Within these four cassifieations there are many vaiations, each ‘with 2 unique set of properties, Paper and board isthe largest single ype of material used for packaging — 34% es shows in Table 1.2, Such estimates ofthe ‘Worlds contumption of packaging tateial are necessarily “able 2 Word pocket predcson by ea and mgs, 1985 Estinted annua timated annual valutafpsctoaing, —_quanty of packaging, uss lion salon tones ips ado 10 500 37 Fes wo ko 2 Neat mo 1 Gis ee hes oS ‘al ase, ‘Seare Wavd Pohang Oriani by How, M Wid oagng ‘Soe Pasta (197) Impress and ee likely to exclude many ofthe traditional mate- ‘als which areal used toa significant extent in certain ares of| the worl, for example re-used paper and natural materials such, se bamans lene, Plastics are a close secon, representing 30% (by value) of world wide packaging production. In recent years plastics have been brining markt share athe expense of al other materials Plastics te the youngest ofthe packaging technologies and are sll very ‘much on thee upward grows curve. ‘The properties of plastics have progrested avery long way since the fist one was developed over 100 years ego and most of this has ‘oceurze since the end ofthe Second World War. Panes sre now ‘rllbie which have the piysicel strength of sel te emperstire ‘esstace of aluminium, the printabiiy of paper and bacier Drop ties approaching glass, Altiough some ofthe more specialized isles developed fr engineering applicasons are oo expensive for peckaging use, there ie ise doube thar some ofthe materials now being developed wil allow for wider expliation. Tis book ex plores the commodiry packaging psi aswell as some specialized ‘pes which ae finding new packaging aplicains “The choice of packaging materials depends on the characteristics ofthe preduct and she expected packapig performance, The pur- pose of packaging is to protect, contains kentfy and promote is ‘contents —as well as delivering them in wsefl form — often fo 4 single use Packages are algo expected to facilitate product use Including being easy to open, cspense,reclose and discard. Environmental concern ver the extent of packaging connump ion sand disposal slo a major factor considered by packaging peofes- sionals ecking 0 conserve matziais and reduce slid waste “The purpose ofthis bookis to provide a survey of packaging mate> al. Te describes ech packaging material, cscusses the material's properties and applications, and indicates disposal options. It Focuses on the ecient uve of materials, because reducing and conserving packaging also make good economic sense.6 Packaging Materials Strategies to reduce and conserve “There are a muimber of approaches that may be taken co reduce the cost and amount of packaging material used, including sb- ‘ciation of materials, ennancing material performance, reducing tersp and teressing process eficlency. ‘Although some sdvertsing-oriented strategies may increase materials urage in order to provide more product fearucs or ering spe (and thereby increase sales), the alm of mater- tls eduction is economy. Every penny saved in packaging cos _mslipies into prose because of the high-volume production of ‘mos consumer Eoods ‘The frst approach is the rational evaluation of substitutable material: Te history of packaging isthe story ofa progres Of materials, from the skins, baskets and pots of primitive [nunterfgatherers tothe olouifl plastic forms that prevail in 8 modern supermarte. -Bvery new material is seen as a potential substitute for one oF rote of the existing types in use. Disposable packaging has Sivays been made fom the lowest cost matevileavallable ro culture, As new, ower cost mera are commercialized, pack fgers have found new appicsions for them. Sometimes there is @ perfect match and substitution rapidly ‘occurs, For example (as decribed ip Chapter 6 und 11) oven ted polypropylene fi rapidly replaced many cellophane spplica~ tions because its properties wete superior, ft rune well on the ‘same equipment and its mac lis expensive, In other situations there are limitation which make only pasa subsitnion Feasible. Plastics replacing glass and mel fr processed foods is good example, since food packages need bet- terbecies and heat resistance chan mos planes slone can ro ‘ide When each a compeive threat aie, provides a apr co ‘development af bach the new and the old materi ‘The seein and eof packaging materiale 7 Of the four main groups of materials, paper-based an plastic ‘hve experienced dhe most steady growth oer rent years. Met tnd glas are losing shars, having been replaced by plastics ce apetplastic combinations for many applications. One purpose Otis book sto highligh she subeitutbiity of materials used for packaging. [A second approsch to materils development isto ennence the performance of existing material, mating it posible to use less material. For example, patie manufacturers ae consinvaliy researching beter formulations of commodity pasties, like the tse of new metallocene catalysts in the manufactre of pay ‘ethylene described in Chapter 6), improving amon ll of ite properties, Another way 0 enhance existing materils ie by combining the best performance aspects of a number of diferent materiale, each contibutng its special set of properties tothe inal rel. ‘Brampls include plastic coating wo strengthen and prosec lst, sand paperifoilplasic laminations to lengthen the shelf of food products. Chapter 12 outlines some methods for ‘enhancing packaging materiale’ srength and barrier proper, ‘wo of packaging’s most demanding ausibater Chapter 13 dis cusses material medifeations such st coatings and material ‘A third economical approach i o improve materials wtization, ‘ediucing loses duc to faity production and making greater use ofneplant scrap. The relative importance of materials conserva- tion vases among the diferent material yp ‘Tele 1.3 shous the relative siqifcanceof raw materials costs. ‘Metals are atthe top of she scale ~ the materials account for berween 75% and 80% ofthe final cost of a inplate or sumini- ‘um container. Psper and plastic matezas account for about 50% oftheir tous contalner costs, and pass with ite cheap rer materi tls (ctl sand) ia he bottom wih 20-25%,: srocnagong Matera ‘he sic ana woe of pastageng marerais _ fonsinr a 2 ent) Naaurat resources Scrap uslization figures vary with the manufacturing process used ad the lve of technology involved. With metals ane paper conversion, in-plant scrap has tobe collected and retuned tothe Primary material producer, Plastic and glass masufactrers on the other hand, can usually pur eee srap stripe bac into che process to produce new materi o eotainers Likewise lft Ihateals can be easly recycled fer use ‘A fourth impetus for materials development i to keep up with demanci for higher fling machine specdh st product mansface ‘urers' plants. Ar the seme time, manufscurer are developing ‘ast customization strategie that favour short production une sth ick shangeovers, Someries an apparently minor espece of a package can make @ geeat deal of dierence ini ability 9 ran on machines. The flevelopment of cald seal adhesive ie one ofthe best examples, because icallows horizontal form-All-sel tachines tobe an at very high speeds and is now used extensively to pack coufee Honey produce (as deseibed in Chapter 14), External factors influencing the choice of materials ‘There area numberof natural and socal Actors chat influence « culture's choice — is supply and demand —~ of materiale. ‘Avilabilicy of natural resoutees and the sae of packaging tech ology affect che supply of materials, Socal and cultural norms, such as lfesples nd environmentalism, sp well as trends in ‘macketing and cisibution fect packaging material demand. Hiszorcally, people have used whatever materials were realy fvaileble and those which we have had the knowledge and fechnology to adapt. Thus packaging began with natural materi- fis gout anima skin and large leaves — progresed 10 exs- iy worked materials like wood and clay and then on #9 paper, etal and las, and Sina to plastics, Plastis ace guiteeilferent ‘Rom earlier mates in that they are nota sizaple conversion of fn existing meter, but invoive the modification of the basic Structures of chemicals to produce entirely new compounds that do not exist in nature. “The pattern of development, however, has been the same for ich materi om the amall-tcale discovery through experiment to advanced-seale manufacturing, wih the cost falling at cach ‘age. Fr erarmple in 100 years (rom the mid-1800s tothe mide 4800s), canned food went fom being ahuxury good vo the com= ton aa inexpensive proce tat ii today. In that time, che process for making tinplate, reaming cans and filing them Became ves more ficient. [Most of the material resources used for packaging ae either fenewable (wood and vogerable Sr for boxes and paper‘ssed pechaging) or very pes (and for gine clay for crams ito (res for meal, andy nth inter, buusie fr aluminium). Even the finite resource of poole used as feedstock for plas el tively plentiful considering the small amount ofthe world’s oil proicction thats used —tery efictendly — for making plas “The other primary resource sed forthe manutacrre ofl forms of packaging is energy, Four main sources are used: fossil uel shorcterm renemable forms of energy such as wood burning, ‘fee’ energy Gola tidal wind end bydroclectie) and nucleat ergy, Difeent materials require dering energy inp Sale itt sy tha all non-enewable resources based on miner in the earth can be secovered, however much they10 Packaging Mater have been transformed during their ute, provided that sulcint ‘nergy i available, This as led some commentators to sugges that inthe long teem the ese cost ofall forms of peckecing villbe determined by the amount of energy emplayed in thee Packaging also fees dsporl resources, Packaging x about 30% of the weight inte domestic dusts or bag. Resdenl comms nity opposition co landfils and ‘ncinerstion hs made rock options more costly. Reeyeing systems, while reducing te amount of wate are sometimes produced woste encom effets than disposal, including ait and water polation ad high Inthe industiied woe, etc hes been aimed at the pace swing industry by some ecologies, environmental premute ‘rovps and consumers. The most frequen charges ae tht pale fazing makes excesive and wastefl aoe af esouces a othe borden of waste disposal, and vec lare amounts of eneeey including os ela feedstock for plastics Jn recent years, there has been 9 growing call for ll products ‘including racking, 0 be seen tobe rea’ (ue sense to the ‘scological needs of the planet) The packaging industy hes ot slays responded tothe eis ins prouetive mance The ‘manaftcturers of one materil like plas or pape) have tome times blamed the manufacturers of competing rates One effet of such internecine warfare has Becta harden the ara ofthe activist protection groups agsinst the whole industry. Ta some counties, nocabiy ia Europe ad Japa, reyeliag ban ow ‘become mands a any cost, ‘A more productive approach iso understand the ccm and to reduce the burden of packaging whenever practical, ‘Over packaging i costly nd i rarely a succeslal satesy anyway. Producers ate well advised to reduce the resource Used for peckaging, and packaging reduction has long been «succes Strategy foe com retin “The lion and we of packing aerials un jg materials can, techically, be recyled. Table 1.4 ome te rnive reoling rate of aiepal sod waste Sher tan gal nat), Gorvagated reboot The economics of cycling vary by materi The dificult an outage assolated withthe nee o sort materials 0 that they a be hmogenou resiled, Corsten ‘omic! elle in ge homogeneous amount om eales tnd warehouses, and is economical to reproces. However, for ome other materials, ike multemateril barrier Aim maxed is Tninate amounts wth other howschol packaging, the calles, sorting and reprocessing offen uses more esoures than it as artherore, thee consic oven the easy recig of Singlet package nena we o atari fans Mulirmeter pastas, sdough ponding ape peo tection at low cost, can seriowaly impair the economics of Scrap reuse and eyeing The demand foe mote package recycling — legislated in some parts of Burope and Japan —~ ean have an imporant effec the lection of packaging marcas, Materials menuftcares and2 Packaging Maser esgners can greatly affect the case with hich packaging can fubrequenly be collected, enifed and recyled wo proce net inet, bu it maybe atthe eon of ang rates fen There have been some who have promoted biadegradable end ‘hotodegradable plastics forthe amelioration ofthe problesn of lier and for packages that are ulimatly andiled, even hough lle biodegradation actualy occurs in moder sanicary indi, ‘Biodegradable packages havea numberof problem, including the fact thatthe depradation may cesur too soon, daring the ‘fal ie ofthe pacage 1 the pst, cos hasbeen the primary method for assessing pac ‘ging matecas,Envionmentlie cots have argued tht ead onal internal cost snaps dors noe nce the external cos oF lgposa and pollusoa tater borne By sci. Lite unis (LCA) ie # new techigue tht i sin Power aba method to evaluate the burden of pachagiog onthe Seventies i account ‘atria extucon, packaging ate conrenians pack fling produ dseioaon snd paclapiog dpa reeing serum, I'consder the fenemabiity ef trl resoueon at el &poltion ees. Tis ‘rade to ge approach can be tac Tecompatingshernae packages, Demographic and market shifte “The market shift that has mos affected packaging isthe change inthe emit century from stall real sores with bef ot, vice assisant wo sell-ervice shopping ia large hypetimanets ‘most etal settings today, the package i enpecte tobe et trating attention, inking seal shelves to media advertising, and conveying important informacion such snus Sonal conta snd warnings. Pechaging faites self-service shopping and the ute of al kinds of consumer products, fem food to shampoo te voy. Aateacne The ston and we of packaging materials B materi ike holograms, are used tlie shoppers and eas ase features ik easy epenabilty and resosabiliy tend to make ‘shoppers brand loyal ‘ur the advertising function of packaging has Been blamed for fecetve ae of packaging meal, a some manofecrrers have ‘oloited shelf-facings by making packages as lage as posible. Increasingly, consumers are not foaled by tis serategy. They ‘complain that packaging adds uanecesurly to product costs, ‘hata imi consumer eoies, that fe may be used n a dep tive sianae, and that I appears a8» maior consttwent of ier sd andl rckaging decision-makers must weigh che benefits ofthe in- ‘Store ilboar flac, which ia the past has been shown to atact sntomen, agains the growing demand for more eien we of tater inthe pat fw years product concentation ané packs ‘ging rection stents nave been gscing maser share, “The ssond masher change with great sanfcance for packaging fs demographic, There have Deen huge changes in social putters ‘recent yen, and while tene are a diferent tages invari: Dart of th worl, the general rand isl able at eitferent aces “The largest segment ofthe packaging industry deals with foods. Food mantactarers are the mor ensie to changes ese find demograpiy since the changes affece and are afected by, {he ey that ween and prepare food. More women now are employed outside she home, ano here fan inesasing demand for grester convenience in food prepars ton, More of the populatgn consists af sgle-person house= hhlds and family mesis have Become les common, increasing the destand for eay-tosrepare single meal. Coupled with the dyna grow ofthe mieowave oven, these changes have led to huge gonth in demene for pars oe fully prepaced meals find enacks“ Packaging Matis ‘Such convenient refgerated meals necesstedifrent forms of packaging, often involring very demanding performance to Increase shelPlfe, Longer selfife can be achieved by sing ‘materials with superior buries properties (0 wer, oxygen, bac ‘era. In the ease of sh produce, mates ae selected t mod iy the atmosphere inside the package and slow the products “The demand fr miceowavable packaging har also rimilted the development af het resistant materials that ae dus-ovensle, that ican be heated i ethers micromave oe & conventions fren ace microwave ovens cannot brown fod, sealed ‘se {pte mari te oral mca tary Ho ou ‘Another important demogrephic tend is the agin population ia ‘an pars ofthe worl. Older consumers hate spect! needs for ‘rode information and ergonoaedeians, petal with regard tomesicl produce which sre more elfen uted by oder peopl “The near future holds a third marketing srend chat at ignif\eance fr packaging. Consumer’ dese for convenience creasingly Belay me: by home deliveries of predate oedered by ctlogue or computer Clothing and home furnishings are slecady widely ordered by malin some countries expec the USA). Home deivery offamoving contumer produc i being tested in many places, and is predicod to grow Hlome-detisered peoducts wil tinue sme interesting package Ing changes. The package wil pay a dierent roe in silting shopping choles Packages fancton less to act shoppers fot the inal sale, bu wil be caled on more to reinforce puschase decisions and encourage the shopper 9 buy agai. For home dalivery of foods, shipping containers may need to be insulted or relagerted Home deiverice and other logisie advancements stimlate oer changes in shipping eontaine: design. The new s0pply ‘The slesion ad ie of packaging matrals 1s ontsinessfacitate prodct Row throagh sorting opersto. ‘oh shocter supply chains, cers less warehousing, inetoding ‘Notsge and order poking, Orders ae shipped direct from the fanafacturer so the rear, wih simple sorting operations Secween. Such stin-time systems can cteae opportnities for ‘ore efficient shipping containers. For examples they can often Justi in economic tems the ute of enable contsnet. For direct detivery, whether toa home, business of retail tore, sipping containers need to be eas to sort using automation Tnsuch care, packages need to have standard dimensions and ynaterias (generally corrupted hibrebosrd boxes or reusable ‘lst te) and barcodes nee Gen x tana posion Global technological developments Packaging is a rly international stig, Marketing information technology and lists infraseructres now lle sourcing to take place on global basis with packaging Being done atthe ‘ost eatianal point in tho supply chat The packaging iadustey, within counties and across borders is experiencing along petiod of restractring end consolidation, Teading to polaczation of both markets and. companies, Inrernationl pastagingrupplycompanice nave developed ead” ing to prem standardization of materilsseros couris, At the same time, there are opportunites for small supplies to exploit fszegrowing niche mazket with igh added value potenti. Although social, timate and merlot situations ditfer widely technology iv readily transferable around the word. ‘Those involved in pute packaging ianovatons consider the world us source of inepiration and informavon. Many would agree fat Japan represent the mejor een of shee innovation wale fhe USA and Europe concentrate on fewer but larger-scale develope16 ockaging Mate In Japan, packaging is both an artform anda scence. Ostng 0 their cultural background, Japanese consumers seem expecially 10 appreciate high ql and novelty packages The gt ing ‘don emphasizes high quality presentation, ad packaging i important ashe em is fn order achieve pu novel often forts own sake, manufstarer: wil offer a bewildering range of ‘packs to temp he purchaser neo buying especialy where market Drestures are high, a the beer and soft drake sectors. While ‘ther markets may not eee this level of sophistication — or ‘ay consider we ponte wartefl — the technical devslop= ‘ments such athe sl atiag sake cin have fund eses in ote packaging tuations ike the selheating dinner for driver, Packaging plays significant role in nation’s economic develop ‘ment. It mereses the protection of domeste godsend enables {hei export ito new marke. General the expendicare on pale ping it much lover in less developed counties, Most materials Sd graphs are less sophisueated, bt the packing tat ext {generally economical, material recovery aysteme ats efficient, td "ete are many creave packaging appietons using indigenous ‘materia and appropriae technology When» country decides 10 ‘expec is gods, usualy fn he need fra package redesign 0 inereseprsertion and improve gap communication. Requirements for selection of packaging materials Given the wide range of ubaiarable packaging miter ‘ment and public raion. Moet glat bottle are formed in 2 two-step blow and blow procest A gob flit pass dropped into Use mould and posed {nto the neck, caled the fic. (nhnd-lown bots, the fis tin the lt part formed in modern bote-making machines, cis the Sis) Airis blown ito de fish in a vvo-stage process, fst Blowing testtube shaped parison, and next seherting and Slow Ing int the parizon sel the walls conform tothe mou evi. A pres and blow proces used for wide mouted jars where the pasion le formed by a plinger Mtr forming, anacling in 28 ‘ven i equted wo relieve steses a result of moulding. Je, ampules pipettes and very small bottles are made frm, ‘ae bing whieh s made by forcing molten glass rough a de ‘The ming rimmed and glazed in a separte operon Lightweight and strength improvements, “The economics of lets containers are dependent on weight ‘Weight ie seltec tothe amount of raw materials nesded os well ‘eto the dstbution economics since freight costs are direcy dependent on weight aes ef ‘Therefore, lighowsghting, without sacrificing strength, a ong ‘been godin glasmaking. The UKs returnable one-pnt milk bottles been progressively eeduce in weight fom 600 gin 192020223 gin 1998. {tis well known that gas isan enormourly strong materiel even in very thin sections (one hat only to tak of glase bre reinforcing flaments andthe common elect light bal), ses ‘theorsialy posible to mate very thin contnts in glass ‘The weakness of glee i hat it rile and tends to have ts stress locked ies the rurfae le, Ifthe surfaces damaged tt all the material ean be easy broken — which fs how » glaier an score and then snap a tick sheet of pars between his o het ‘Angers Likewbe, a scratched plas bottle fled wich presnurzed ligid can becom dangerous bomb when dsopped. ‘Much research has therefore gon into the four main routes to minimize this surface damage factor in thinner containers. + reduce ern sressess + minnie sce esos + coat the surfs; and + use protect abel, “The internal stresses canbe reduced by design changes which fesoltin better dstbuten of glass and improved saaling con two, Since glass a supercooled guid, i cam cool a difering ‘tes acording to ai currents, varying wal thickness, conducive et eo oe ppt ular nd the proxy af oe hot or example, high stress concentrations in tharp transition Fetions tend fo euce «boty strength a bore witha smooth vertical profle is atronger that) one with sharp tansitons,2 Packaging Materials Simi clinical bot usually stonger than areeang- larone. Computer modeling shows that balanced design of he shoulder, heel end bottom regions ean contribute to stength Better understanding ofthese complex effects has made i posi- bet reduce boule weights eft ‘Exenal surface blomishes can be reduced by cael manufac ture and handling of the moulds and by equaly careful handling ofthe glass parton and botde during manufacture and dsteiou- Won. This ie an important factor to consider inthe design of ‘mule bates. An anal ofthe olnt of contsc with ship- Ping containers guide rail, bate support closure and labeling ‘suipment maker poale ro build in ‘wear absorbing’ zones of Strengthened sections. An example which allows for absorbing ‘wear to dimple the contact surfaces Casually around dhe sides tnd base)s the high spots will be rubbed away sau controlled ‘anew minimum effect onthe overall eng “There are two Kinds of srface coming arable, depending on whether the coatings applied on the hoc end o the cold end ofthe Sott-maing proces. Hocend treatments toughen te ote skin. Cold-end surface teatmenssiubriate de exeral surface, Both ‘ypes redace the possble damaging efits of the lasetorgass ‘contac which ae navoicble drag norma ling and use ‘A combination coating of no titanium oxide followed by PE is {he moot usual sorsteh-exetane coating. Alternative cold-end coatings are based on polyurethane, epoxy, scrylystearaes, ee ei, cones ad waxes. There ean be bonding problems which est inthe coming coming inc conact withthe fod. Some ofthe cold-end testment are removed by the alkaline wash water sed in rerurnable systems (or example, as used for ‘beer and milk in the UIQ. Some reuraabie systems have expe sented wih ecoating the bots ater washing Other creative surface costing ype modifications include: usa ‘skin layer ofa diferent kind of slats onto the bottle exeror, modifying the surface chemistry ofthe glass and atherexperi- ‘ental costings? Some rorface treatments and coatings can also ‘be used to change the colour or surface texture, a Tec ‘which ered extensively in Japan. One examples double coat Ing of plastics (@rndename Mul--Cote from Star Chemical in Japan) stone butadiene rboer followed by a sinner layer of ‘igh modulus plpuretane which may be coloured. “There area numberof protective sleeve abel solutions tothe damage protemn. The mort common is + foamed polystyrene (PS) shrinkable sleeve about Imm thick, covering the street treat from the thovlder to under che base rim (@radename Platield, which en be printed. Inston to surface protec sion an the ably to ightweght the glass bor, other benef Jncude reduced noise during filing anda beter and safer grip forthe consumer wits some degre of thermal protection. Polyvinyl chloride (PVC) revere-priated shrink-sleeves have been wed in Japan for 20 year, and more cently have expaid+ into Euspe andthe UK. Th abe usualy printed, bu can tho include an overall colour to convert clear glass botle to an Spparely coloured one. Resenty selective metallization snd fol lamination have been added the oprione. In addition to protectiag the container from surface damage by elase-toslast contact, an important function of the double ating snd the protective label Soludons sto prevent dangerous ‘Saterag of lame shards presurized bots dropped New developments, Research fa coming and swengthonng techniques contin bat thee tore empire now in marketing. The glass bore indus ty has survived, but ony barely, the competion from plastic fand metal cuntlaes.Tnplae and aluminium cans predominate {nthe beer market, and plestic has epaced glass fr soft drinks, ‘water and many othe bod produc.u Packaging Maries ‘The gas industry s concentrating on the matic ches where i provides a compesiive advantage, lke premium food products fad for redlable bot applications. ass bots are sil the ‘ost ice for rfllable bots and canbe cally recyad. “The industry has puta rest deal of effort end resources into ‘encouraging the recycling and revse of las botes, This en- ‘veonmental factor euld be te mot signa forthe fate of ils packaging, rnce some counties are legislting the ure OF ‘eflable anc reyclbie bots ‘Ocher now developments are related o improving plates with « ‘material chemically salar to glass. Scan oxide can be vapour posited in en ule thin ler on the surface of plastic eters, resulting ina fcibe mei] with nearly the poperts of gas ‘This described in more detain Chapter 13, Similar in some respects, but diferent in techaology, is the esearch into agvel ways fo produce continuous layer of ass ‘ng a cold precision process A solution of eerseduxyeane snd water is heated to produce glassy lye insta. ntl appi- Cations have concentrated on very chin layers for microchips bat ‘teoud have packaging splcations inthe future. 4 Metals ‘The most imporcant mess used in packaging are sel tn and sluminium. Tiaplated ste fod cans and slumisiusn bevecage ‘contines are de most prevalent applications, Other metal packaging applications inclade tee drums and pall closures strapping, tay and ae thin fol bree ayer in lamited materia. In these applications, meal is coming under Increasing pressure from plastics materils which have inrent advantages since its eaber to produce complex designs lke Closures from plastics, and plates are relfcolousing aad dest sealable, However, metals ave performance advantages of their own, OF all packaging maternls, metals have the highest sbeolute perfor: ‘mance in heat tolerance, physical strength and derail, bare: tnd absence of favour ot odour, sfinns and deafold. Cans hve the added advantage over gs botles of easy mast ‘handing without breakage lightfstnss, and the ablicy tobe Produced and filed at higher speeds, ‘or diffrent packaging application, the importance of each of, these properties vare, and Bence the rate of byte fers ‘similarly. Por a nunber of product, ike beer and canned food, ‘metal remains the material ef bole in moet counties, Cans ‘Tinplated stel was originally uted for ta and tobacco boxes and canisters. Tinplate sanitary food cans were developed in the etsy 1800s, shorty after Appers invention of canna’ the 556 Pochaging Mater retort food preservation method (whick orginally uid ass bot, ‘Cans can also be made from tn-free ste! (black plate and chromed plate) tnd aluminium. Tn some couatres, most Beet Sod oft tins ens are made rom nmin. ‘Tinplated steel and tin-fre grades Stel is made from icon anda small amount of carbon, whichis ype nurses ean Be separated for eyeing “Tinplaedstel can stock is made by hot rolling and tempering the steel sheer ton standatd thickness. Tempering determines hardness, and several grades of smper ate avaiable. Harder rade arc ured for can end more duce grades ar wed 1 e= fe shapes, ike dawn cans (desorbed short), Bare stel ross easly and unprotected black plate canbe uted ‘only for non-corrosive products Uke wates and oie. More com ‘monly, inplate i electrolytically applied ina very thin coating. ‘After trimming, mos ofthe coed zeel stock coated with ‘xpaniclcquee to further protect these spain corroion The tinplate and laoquer also protect the ron fm being daved in fod prodot, which would leave a bad taste Foods that are more highly aca equire a heavier dapat or lac Auer coating (or bos). (The acidity Iva of iguid ca bo -mcaured bys pH value; the lower the pH vat the higher the city) Different toques have been developed forthe packag- Ing of various foods which vary in acidity. The thickness ofthe tinplate costing may not be the same on both sides. Tae surface acing outwards is often thinner because it ls exposed ony ambient omy and not t he soatet Lighrweighting bas then place steady in the can industry. Since 1945 the weight of wtel in @ proceed food can has been Meal 2 reduced by 95% and the tn by 60%. In modern gans, the tin Inger accotns forenly0.40.5% by weigh. Developments in tinplate over recent years include the ute of ‘water-based lacquers for environmental feusons and greater Use ‘flaeguered tines sel ‘Tiottoe ste or electrolytic chrome-coaedstel was developed. fn Japan during he 19608 aca time when tin pices looked et to tise aarply, Te chromium metal pls chromium oxide coating {much thinner than comparable rinpat. Tt produces a bright ‘etal fish but does not give the same degree of protection Susist corrosion at does in so eset the tbe Inoquered {es necesary to remove dhe chrome i order towel the materi tl, whics ie often ned for ean ends where weldabiiy isnot 8 ‘ncern, Simlaiy, « new can-making process (Toyo Selkan’s ‘TULE snd British Steels RBS wadetnaths) laminates polyester (PET) fim on both see of nee steel subeate ‘More significant than the material development ave been those socioed with con manufacturing. By far the most significant ‘ttheses and one which has found ie prestet application in the ‘xebonaied beverage and bee sectors the wospiece can Foc moa of tei history, tinplate ans were mad in thre pleces: {tro ends tnd a body bank. Toeay de side seam is wscally induce Hon welded opacing the vigil lead-based soldering. By com> periaon, welding saves material Jess overlap is required) and products stronger seam, which Is important for pressurized Containers ike aerosols Newer welding techniques include the tse of eloctieal induction and lasers whieh permit an increase J production speeds. For some products the seam may be ‘lone sier than welded or sldered, “To complete the trco-pecs can, the two ends are seamed onto ‘relded body cylinder, one by fhe cam-maker andthe second aferse Pacaging Motrin Metals 2 "exert inground Farge on conto iveouee™ ~ soa filing. The double seam includes «sealing compound, shown Jn Figure 41, which i eral In forming the can #003 slight sea. (On the other hand, the two-piece can is made by stamping the meu inthe shape ofa cup, fom a round dze Bank, using very hig pressures and progremive dese files epplis te doble- seamed (op) can end, “Three methods ar ued for making ewo piece cane depending 2 the depth of the exp: drawn, deaw- rears, and dra ad all ‘nuned. Shallow cans, commonly wed for product ie tunash, ‘an be drawa drety by stamping ace into a metal blank, (Cans for carbonated Beverages ae made by dhe drawn ae wall- ‘ironed (enoven as D&T in the USA end DWT in Europe) tech- nique, which involves stamping out deep cup ffom a sheet ‘hich has the same bose as its intended Gnal dimetes, by ‘rcching the walls to he deste height. ‘The wall of DWT cans (especially aluminur can) are very thin and fie were no forthe interior pressure ofthe eabonted com ents (ste drinks are about 3.5 atmospberes or 50 loin’), chee fans Would calapse. Litewise, DWT cans cannot be uted for etored food because they cannot withstand the vacuum. Nox Dresurined proceed foods have been packaged suman DWI cans under nittogen pressure, which extends shel? nd hip to support the eam ws Alrinium cans ate dscused ia smote depth short Deaw-redenw (DRD), a more versatile spprosch, uses more ‘metal since an oversized cup is frst stamped out and this then resid by stages into derper, narrower stamping des. As = Eesul he walls ae thicker and moze uniform than DWI cas, DRD cans are made of electrolytic chrome-costed ste! coated ‘vith enamel and eat be ute fr food, ‘Two-piece can eehnology reslis in considerable savings in ‘material beoause the walls ar dinner Ths saving i fmporant, because (es show ln Table 13 above) mel accounts for most (Gout 75%) of the cost ofthe can, However round omorpicce blanks lave sigaificant amount of warty whereas thee plese ‘ody bianla are square and esult in na ware (ut the ends Jo, hence one ofthe incentives o ute salle ends), ‘The most commen non-beverage product sectors in which 1wo- plece cans sre used in the UR and USA ate pot foods and baby foods. There i a age investment needed for high eapacy peo duction of two-piece containers, and they are pearly avalebie Sn standard se A frther example of mata saving i athe edeson indir ‘er ofthe top end. The technique of neckingrin was developed Jnitly for the-piece cans to eliminate dhe projecting beads atthe top and botiom which gave ise to de phenomenon known 4s tim riding’ in transit, and resulted in Seung, deats snd, Sometimes, leakage ‘With che advent ofthe two-piece ean it wa realized that necking Jn could be taken farther for economic seasons. Making the {hicker cap end smaller erults in the uve of lest material es Seaming dine, and ls losing 0 gud filing lines. he highs speed production ecanomies of canning are such that small per- rclagetavings add up quicly.a Pckasing Materials Mest aerosol cans are made from input n technique i to heer cn poche a done ms ‘ert at appli wo the boy Wh double ses td shipped {8 the ler, Some areas re onde rm hasan 2 oe piece DWT proces ‘The scrosol can is pad filed with dhe produc ales insert sate losing ring, The containers are seared ina manner silar {otha wie in can macucrring. Endnotes for Part 2 1 Johansen, R Favorable condsons for plas costed less bor. ‘le InP Vol 14 Nos 6-7 (1993) p 25 2 Doyle, PJ Recent developments in the production of sronger la containers Packaging Belnaligy and Scone Vol! NO 1 {4988 pp 47-53, 13 ‘Defending the ste en in Jopan’ Gan Technlogy Iernasonal ol 3 No & (1996) pp 22-25; Laminated cans for new mar~ ‘es Carer une 1997) p 6 44 Nitrogen stabilizes thin-walled containers? Packaging Report, [N09 (Sep! 1990) p30 55 Lindsay, D ‘Shaped to sll’ Beverage World Vol 116 No 1635 (G5 Mar 1997) pp 91-2, 94 6 Brown, M ‘Heinen shapes up" Cammake Vol 19 (Nor 1997) pp 18-20 7 Newman, P Just one look’ Ganner (August 1995) pp 32-6Part 3 Synthetic materials5 Introduction to plastics “The word lati deseibes materials which can be made sft and maleale, capable of blag moulded or shaped, which ae ten fixed by Renting, chemical reaction, or cooling. As such, most ‘aterials—inciuding clay, metals and glass — can strialy be ‘scribed as ‘pani’ materia Tis erm is now red, however, te describe synthetic material i the ability tobe formed into Useful shapes by means of heat —a shortened version of the ‘word thermoplastic “Tue frst of what we now call pasties were developed by Mr Daskos over 100 yeare ago Soring the search for subszirues for rarac decorative materials such as iors, ebony and vortaise Shel The early plastics were mainly of the ype known 2 hes Ioset pati, Ley those which once moulded ino the ial form fd set by heat canaat be sibeequently softened. Dusing the 1330n 10 19500 ure became the major pes of plastls Bakelice is the best known name. These materials, based on phenol formaldehyde urea formaldehyde or melamine formaldehyde, found applications in packaging manly as rigid closures and fits since tel brtenes and forming limiaions made them tunsulmble for most exetners aly four thermoset are sil wed to any extent in packaging Phenol formaldehyde (PF) and ores fOrmaldetyde (UF) ae usd int for botle closures, UF is resistant ois and solvents and [food inthe eotmetcs dusty; PF fs sed for pharmaceutical Closures because if more fesittant to water. Both PP and UF ‘lowutes have besa largely daplaed by polypropylene. Glass- Feinfoeed polester, another shermoses, has been used for sor~ fge fas and large transit contuners. Polyurethane, wsed in fam cushioning alo a thermoset7» Packaging Macrias Regenerate cilllose fl (aso known a cellophane) i also one ofthe oldest synthetic materials, tt doce not quay es «plate ‘material onthe bai of ether it ovgin or its natu, a deserbed in Chapter 11. eis derived from natural celuloee (wood, primar Ty) and ic eannor be moulded since ita be manntactued only 45a tin sheet. Since tis nzurl ellie, fedoes not sofen wih heat, bt chars ike paper (alae isthe east way totes fr), ‘ther than melting like peste. Tey early name was “cansparent paper. ‘Thermoplate (as opposed ro dhermort) materials were devel- ‘oped during the 1980s, Celso elulove nate) and etsone scctie, derived from natural cellulose material, and Perspex (he tadenanie for polymethyimethocryate) are examples, but thei sein packagg wan inially very esticted, From the 1950: on, thermoplastic materials bectme more widely sallble and she chemical term polymer was adopted. The Word means literally many parts, fering fo the linking together of ‘monomers, smaller molecules, in chalns. ‘The arcangement of molecule chain affects the properties of the ‘material IF the cin are randomly arranged, the pas called smorphou, and is iow density and stretchy Tf they st ined up parle the plate ie called crystalline and = nv siller snd of higher density, Poietylene, for example, cn range fom high to very low densiy according to ciffereatarangemeats of the same moicoles. ‘Thermoplatics are by far the dominant frm of tl plastics in use today. They ate all bazed on organic chemistry (because thet Tong chains of carbon atoms can bud wp into giant molec) tnd at present they ae virally ll derived fom petochersical feedstocks — mainly erude oil. They ean i fact be produced {om other organic sources including wegtrble materials but at ent economie factors make these of marginal interes, ldough is the long term they wl probably become sian. Freedom plaice, n Most of the maior polymers ate derived from simple gates ke clene and propylene, the molecules of which joi together form polyethylene and polypropylene respectively. However, the technology to split the petroleum gies into pure monomers {ike einyene and propylene), and to induce these to polymer- ‘ae, under de influence of pressure and caalyety into sol imatrils (ike polyethylene and polypropylene) complex and expensive. Only the ready availabilty of the aw materials and the economy of large-scale procesing make the materials 20 low ‘There are about a dozen plastics matrsls commonly used ia packaging, prodaclag a specrum of properies to match mort needs, The principal ypes of thermoplastic used for packaging tre polytlene (FE), polypropylene (PP), polyiny chorise (PVC), polyryene (PS), polyester (PET and PEN) and poly- amide nylon). Chapers 6-10 discuss hese commodiy packaging lasts end ele polyners ‘Tale 5.1 estinaee worldwide plates consumption at 151 mil lion tons by she year 2000. The materials with te highest pro- Adution are low density poletiylene and polyinyl chloride. Polyester tthe fastest growing. Table 5.2 ows hat the poly sanvenes constitute the largest proportion of polymers used for European packaging In ado, plates canbe combined in many differen ypes of stroctures to provide levels of performance aot avaiable trom sty single material, Chapter 19 explores composite flexible materials nd their unique properties. The pestis in use coday have been “round for 10-50 years and ean be combined o meet most of the needs of packaging “The mui imitaons of plastics are i barrier performance and heat tolesanee. A polymer offering improved performance in there particular respects at an acceptable cost coals end the serch for the"iea ingle pate materia2 Ire pls n “The fd of engnserng pac stively coms research in eppi- ‘aon th higher performance demands. Research into these can “Sometimes lead tote development of new polymers aperopeistfor packaging wie they em len o ew prodcton methods which Fakesomeof the ero expensive engineering mail sealable euch lower coms an hence able tobe considered for wider Spplicaions such as packaging, Chaps 12 describes pekaging ‘Spplaions for rome high perfomance materia. Improvements in performance or usefulness do not necesserily requis the dewlopment of new polymere. There ae any varie fone sod permutations of the current plastics which ean extend the ange of wel applications 38 3 Performance-enhancing developments inciude process modi featons suc a thease of diferent eatalyte, combining to oF ‘more monomer (0 frm copolymers ata blending of eilferen mates. Thee i Dermutations, combining anything te arcs (lasso nat-plastio) in some form of maliayer Orblend structure, ths allowing the bes properties ofeach wo be ‘mployed in the mont econamicl way. Chepter 13 discuses Inultayer strsctres blended ‘Additives can be used toad specific properties when needed Some examples include ntfogging agen, antioxidants, svat colour, lame retardant, foaming agent, lbricans, ‘ould relate agent plarcze, heat ane wlevile stabilizers, hd surface restive agents, Fillers (euch a plats and msnerals) nd reinforcing materials (ike fibres) are also used to impart specifi properties, I is ako posible vo modify the properties of abasic materia ‘her feas been produced — either in polymer form or in its ‘conveced form a fl or container. For exarple ira fen produce cros-lining o strengthen a material asthe long ‘molecules combine at various pints to farm a strong three= ‘disenslonal matrix, Surfaces ean be modified by exposure to ‘Shc: Bins Cosmuann Compan Gap 197-199 Te Dig Coprnion pem4 Packaging Macros reactive gases, and even het or suetching can dramatically alter the physical properties of e paste material, For example, iti ‘common fo fame west a plate sre to fcilate printing. Plastics offs some vitally important properties for packaging “They ae lightweight, tough, water resistant ines, iygeniy ealip formed into complex or very thin sections, virtually unbreskeble, ‘vary from highly transparent to bright coloured, and ean be Teprocested ater use of incinerated to allow rcnvery of much of thei energy content ‘Akhough cilzason existed without plastic for millennia, thee i to doabe hat sven the present pater of ving vastly greater mount of oie eesousces would be needed if plastics were foray ‘eason no aralabe. The German Passes ManvfacrrersInstte (GV response roa high eel of ers eptns pst, has produced an asessment of the impact whlch the abolition ofa plastics packaging would have on the German econo By alo: ‘ating appropiate sernative materi for each of the pastie ‘mateils curently use, st ennseratively projected th the total Cconsumpdon of materiale would ineeuse ematical, by four times as mach. Furthermore, eneiy consumed would double nd ‘hevolume of vaste Would doube toa ‘There is no question thatthe use of plates for packaging will 10 inthe future, Table 5.1 sbovs shows that all lass were especie to grow by at east 4.5% from 1995 to 2000, with PET. ‘crpected to experience the highest promt Plastics processing ‘All dheemoplasis are melted by hent. Presure mals them ow land take on new forms cooling sets the shape. Scrap, defective product and used pestis can all be remelted or recycled, Tae easy formbity and economic ecovery maker thermoplanics popular for pechasing applications rosin lates 15 ‘Age the plastic resin s made ino pallets the fee stage of pas= ties processing is heating the piste and forming products by ‘ether a continuous extrusion processor the laterite jee ‘don moaldng proces which e decree, In eatusion, polymer pellets te fd into a hopper by gem and blended and forced, bythe use of a serew extruder shrough 8 heated zone before emerging asa continvots fm or tube of ‘molten plastic which can then be eat or blown into thee oo shapes like bottles. A rchematic ofa iypcal screw excrusion ‘roca is shown in igure 5.1, Fr lage package ke drums the ferew eatracr isnot large enough, and so an aecumalater heed ‘ntruder i fed bya plongee ‘or my of the extrusion method, ts posible to produce m= Inger sructars, of coexteusions, of evo oF more polymers, colours end so on. Coestruson can combine material with it ‘ren properties to produce optimal performance. The technique igre 5. Tipe nace%6 Packaging Maura squires only a number of ew extaders (one foreach diferent 3) which can feed thee output ta combining die a force the layers out cogether. Tae molten layers fase a4 sngle materia if they ae compat Filmmaking ‘To mate sheet film, the plastic is exuded einer a a sheet and ‘ast ont cll rol or blown ito an Infated re or babble (Cas fim can be sick or din; the thicker sheets are generally used for thermoforming or are die eu and scored for boxes, ‘Thinner cast fm is used for many packaging apleations. ‘Case ln is cooled more reply than bln fk, and the im is ‘rested primarily inte econ of errsion. Some cs ns we ‘incalyorieted afer extrusion, which strengthens them in both ‘he machine and erese-machine dicctins; a he same tie the procedure makes the film thinner. Orientation can alo imorore ‘iy, moisture barser properties and lon-emperture durability. By conta, Bown film is cooled more slowly by se blown ro Inflate the seamless tube of paste ati is drawn upward This slower cooing allows the molecules to be oriented i all is ‘on, producing e lm with greater puncture resistance Alehough ‘gnoge contel Is more lie, uniformisy can be improved by ‘ing ocatng die. After cooing, te tube actened andlor st and teted up ata cheet or laylat bing. A schemate of «peal ‘im bloming process shown in Figure 5.2. ‘The abit wo het sea thermoplastic fie is one of thei most Important forming atsibutes. TAble 5.3 shows pica sealing ‘anges for packaging pes, A Wide hese-sal temperature range ‘is usally desirable ro ensure seal quality under variable cond tions. Although most plastics wil seal given a high enough text= perature, high-temperature plastics are generally coated with & Dilatic which canbe aeiated ata lower temperature, Spiealy Dre, roucsion 2 plscs ” Figs 5.2 pl i ong ipa “he $a umpire wich pcan beheeel ei atu eerie a ioe ts Paeocten| ed os tr Ryerte oan ‘it tar PE ar OF ait a Wt pss TON CHS Suc: dnp om Sea, W Pda of Pte oi) TPP. BA)Ql neo a fo 78 Packaging Mails ruin to plsicr ~ Rigid plastic moulding Botes are manufactured by a blow moulding process. There te chee pes extuson, injection and injection stretch Blow moulding Extrusion blow moulding is smiar to glass bote blowing. While sills a thick hollow tubule extras, called « parson or pre= form is cmped beeen to bales of @ mould and ait i then bow to the neck The bore ie cooled in the mould snd trimmed. Only the outer euface exactly inatches the mould end ‘we glint othe precson achirabe ong eo this etc, ‘Most pasties can be extrsion blow moulded, inchading PE, PP and PVC: Tes the predominant proces for making spall Irge plastic containers, upto large tanks. Most common detergent [nd mi bones are made by tie poco. ‘Bote having two or more layers of material can be made fom & coextruded parison. Tis common to use reycled material in fuch sandwiched constriction, withthe reveled plate being Alanked by virgin material. Soc constructions eliminate possible product contamination ffom the recycled stock and enable the ‘se ofa standard colour forthe outer package. Another applica tion isto sandwich a layer of edylene vay! alcohol (EVOH), @ ‘very good oxygen barsier bur whichis susceptible ro moiste, between two lajers of good moisture barrie In sore cats, fe or adhesive Iyer mat also be incorporated to improve the atria: t-matera bond ‘The economics of blow moulding (including the transportation ofenpty container) ate such that many bottles are now formed Inger sjocen cs he Ecity tht fils and abel hem. There are Inoveasing eforte co integrate theve operations. In new espe blow-fllsea! processes, botles are blown, filed with stele "guid whe sili the moulé and then sealed with «heated die before they are ejected. Other asceptic systems are evalable In which the inherently stele bottles are ceed a the point of ‘manufacture with «thin removable diaphragm. This is ce cut bff under asceptie conditions atthe Ailing point. I-mould labeling is another interesting variation in which a printed label ith besc-actvated adhesive placed int the blow mou cavity ‘and bonded tothe expanding hot parison. Injection blow moulding adds precision ro the betle-making proces. Iebegins with an injection moulded rabe shape pasion ‘which hen blown into a second, fullsize moulé Since the neck injection moulded, dimensions ate more pre= ‘as an important featoe for complex child-anstant and enop- tn closures The injection blow moulding procs ie uted moy forpitemaceuteal and cosmetics bottles Because they are seal, snd predse neck fishes ave important Injection stretch blow moulding is used to produce the large umber of PET botles vse fr carbonated beverages and wate [An injction-moulded parzoniseated toa temperature which just barely allows the parson tobe lasted and align its moles Sar swucture. Then the materi is heat ae stretched by means of s pneumatic rod inserted itn the neck before Being blown Inte the mould (ee Figure 3.3) “There are ow alternative proceaes available, ln the single-stage proses the residual heat ofthe original moulding process = evsined inthe preform and itis steteh-blown immediate In ‘he two-stage proces, the preform allowed 10 cool andi an ported 10 the point of use where is reheated and Blown into ‘Sonerners at he filing sit In sretch blow moulding, the plastic is srengthened by bil rietaton ofthe molecler, which improves stength, arenes los, sites and ges barrier performance. Athough ‘ort plastics are capable of orientation, PET end PP (and to & lester extent PVC and PEN) are most commonly procesed in this manner,“ Pea ris wares | [om rots tnt Injection moulding Is used for making clorures, wide-mosth ‘ub, boxes, complex shapes, andthe parsons for injection Slow ‘moulding. The molten pastels njeted under presrure into & fully detailed: mould. The mould has ewo pares which are ‘clamped together during moulding snd then opened to ces he Jtem (ee Figure 5-4). Highly proce cimensons very fine dea fd very thin sections are ll pnb sing tin techn “Thermoformed containers and parts are moulded from extruded sheet plastics Thinner (05-20 mmm) matecais ee made into Distr, cups and ways by «continous websfed proces, Thicket ‘terial (1.5-13-0 mam) i normally shoe fed and sed 10 make pallets and dunnage tay “The sheet i softened by heat and then foreed aginst a moulded shape or cavigy using air pressure (either vacuum or positive ‘compeesied athe formers ited to I atmogphere) andor by mating matching moulds (gee Figure 5.3). Then the material {8 cooled snd trimmed. Since material dietibution is dcectly related tthe parts geometry, a phig aril soaelins used 19 Jncreateuniformiry, especially in he corners, which iaveriably ‘ouse the thinnest section, nvodsction wo plastics a te — |S ea igre Stine oun PES sata ld Figure 5.8 Tharasening Foamed pletice are formed by dispersing bubbles of gat fhrouphout a fuid polymer and then stabilizing dhe esuling fellas structure, The material can be extruded in plank ot injecion moulded. Foamed plastic aplication range from flex- ble food cays and eushioning materials to rigid structural foam palerboxes.2 Packaging Maurie There area numberof hybrid systems in use. One is slid phase presure forming, in which moulded and shaped preforms are Feated and soesched or thermfrmed, This allows the die ‘om of macerial tbe controlled inthe peform rage 0 that the final chermoform isa uniform as posible. Another hybrid is rotational thermoforming, where 4 web of molten plastic is ‘trued drety onto a rotating series of moulds in «centnuous process, Advantages are more unlorm wal thickness the cone talncrs have less thecal strain Sul nto them, and tome very igh output speeds are possi, nly one plastics forming process does not soften of melt the plastic before enters the mould In rotational moulding, finely ovrdered polymer (aesaly HDPE or LDPE) is metered into 2 ested metal mould which f then spun around fr roe secs divibate the plastic at # mets The material adheres to the ‘moulds walle and fines into = continuous layer. Rotational ‘moulding i quit slow: relatively crade sheot meal moulds ay be wed andthe proces inmost salable for large ies and iner= ‘diate bulk continers, Recycling ‘By definition, most thermoplastics ae easy to recycle by emel- {ng and paris rer hat nba been recycled, Plasdcs have 10 ‘ne orted by typ, however for reeling bake imo the arial commodity value meter. Contaminated or mixed plates can be raked only int tic, lowsalee mater “Tobe recyled,por-consumer pass have tobe sorted by Ne tnd clout and sransported to procersing plana where hey ee ‘hopped aid ground into fakes which sre warhed and mclted into pellets. The US Society ofthe Plesccs Industry (S21) has ftandardived a coding system, which is elso widely used outside the USA, for the most common plastic resins (2 Figre 5.8), ‘ne now most bottles and many other costaners include the ode for hee materi. Iroc plies a ARAM Poenire —Hghaenty, nd Lewsey NNN DOS rovpenfere Free eran {eis hls sorting, collection and taneport that makes the reey- cling of some pasties uneconomical id may reset in tore ‘cvironmencal impact than other disposal options It should be ‘ote that mined plastics ean easly be recyled into energy by lncineration, and that in landils they are (atleast for tay sear) ner “The patie that ate most highly ecyeed sre PET soft denks bots and HIDPE mak and detergent betes These re plent- fest recognize and to sort and the reins (eepecally PET) have good market value, LLDPE film fom susich cap and txpanded polystyrene sre reaped in tome communities, Ta Some Buropean and Japanese communities, :eyeling ofa pla tice hasbeen mandated by government. The paces ificeles ofenforcing such leglation, were, may mea tht this aim ‘rs ache, nd eve es eeonorae6s Polyolefins — polyethylene and polypropylene Polyoefns are the workhorse ofthe place packaging sector bechuse of tei wide range of wef properties. They are the ‘ort inexpensive ofall plastics, They are tough, strong and a ood barrie to water vapour Ar the properties of poljlefins are ceinualy being improved, he valve ofthese material in packe fing applications comsinues grow. [As chs name imple, poyoefing ae formed by the polomeris ion of certain ursatursted hydrocarbons knot a¢ oles (or slkenes), Polyethylene and polypropylene are by fat the most Important plyoleios used for packaging, although ozher mem= bers ofthe family such as polybuplene and polymetayipentene Dave their own esabahed tes ach polyolefin is characterized by ite primary building block, with each ssocesive one ia te seves containing one more CH, froup, Thus ethene f Cl propylene is CyH,, and butylene {Gyry, The numberof hydrogen atoms i lays twice the num (Seri cavoon tome, Polyethylene’ molecular arrangement i shown in Figure 6.1 “The fac thatthe stoms of carbon and hydrogen may be arranged ‘in many ferent waye makes possible to produce vriatons 44] asoo % Packaging Maris the properties by using diferent polymeriing echniques end diferent catalysts. There i currently» grest etl ofrexearch in the area of new eatalyss especialy metallocene, to improve the properties of pollen Polyethylene (PE) Potyedyene valued for three properties: coughnes, hens Tait and the barir that it presents to water and water vapour ‘Other benef charseteris at it, i any, moisture bsoep tion and low coefficient of icin, It is generally inert and has ‘excellent chemical resistance aliough itis auacked by exiiing {acids and is permeable to gusline and lene. Polyrthylene has the lowest cot of the packaging resin, Since ‘alo has the lowes softening point of the packaging pasics,i aio as low processing eneray cons The family of paietlencs fa the moseveraile an economical ofthe polymer ceins. Asa result, poletiyenes are one of the most popular packaging ‘mately dees ange fom alt bots to te ubigutows plastic bee ‘The ow softening point, however, makes PE unsuitable fr hoe- ‘i sppieations. PE Aim and bags mvinai hee Heb ae Temperatures, and are used fr tezen feed. Polyethylene is dificult to print and the surface must be fame treated, for rigid conainer,or corona discharge treated in the case of films. Potyethylene i formed of lng chains of C,H, unis, but owing to the ability of carbon atoms to form side branches and the are stions in conditions io which polymerization takes place, the ‘materiel s noc always formed as molecules of standard shape ot the same size, The molecules ae long suagaling chains with branches, tangled together in varios says t form the fou, ‘eanspareat heat-sealble mate Pabaifins — poblone and peyoroelone ” ‘Tue properties ofthe several yper of commodity polytiyiene depend on the density, molecular weight the morphology (ote. ‘ule shape) and the degree of erystaliniy. The primary perfor ‘mance ference among dhe ypes ae in rigidity hen resance, ‘hemicl resistence and bi to eutsn loads. Density i to lage extent a measure of the crystallinity ofthe ‘materil, The density of polyethylene can range fom a high of (0.970 gles to alow of 0.880 glen. Table 6.1 shows the eltive estes of common poets type, om hight ery i TAME Ree dein ofpetieny = Fe a Taos ore peri OPE ome Gieoaars ‘See: Moin Fas Eas Hk McGrew ‘As density incrensc, so do the properties of resile strength gas tnd water vapour barrict,rgilty and temperatace sabi Properties which diminish with inezeasng densty are lai, impact sength elongstion and hetselaiiy, ‘The moleculat structure ofthe types of polyethylene vay. Low lensty polyethylene (LDPE) is characterized by Tong side- baaches hat give he rsins heir eombinaton of flexibility clar= ‘y and ease of processing. High deny polytyiene (HDPE tes 8 more linear structure, allowing fora tghter packing of mote, ules and resulting in a denser, ster shateria. Linear low den sy polyethylene (LLDPE) lack the long chain branchiog of LLDPE and has a narower moleculte weghtcistfbution.Mgure 6:2.shows how thee molecolr branching strates die. Low density poethylene (LDPE) was st produced in 1993 in England by Imperial Chemical Industries, Inthe eatly 19508, PPitips Petroleum commercialized he eatlyte which ae wada Packaging Macrae Fay Towecaly rar ty igre 62H ow sd ine ety apne eee to produce high density polyethylene HDPE), which became the ‘ist commercial produc of extalyie etylene polymerisation. In 1960, DuPont Canads began producing lnc low density poly stiyiene (LLDPE) using a new group of transition-metal cat Ips Tn 1976 a now family of exalts sing mealocene ‘single sie’ catalyts was dsconered, Nov, HDPE, LLDPE and VLDPE ‘ery low density polyethylene) ca be produced by anyone ofa ‘Buber of precests to have are properties High density polyethylene (HDPE) High density polyethylene i one ofthe lrget volume plastics ‘sed in packaging because It ls economia! and ean be formed in ‘wide range of forming process. ezn be: + blow moulded into bots for milan jie; + Injection blow moulded ints cosmic bots; + ejection moulded at caps and exten + extned into fm for use in bag fal kind + thermoformed into rubs pallets abuline — poe ad plypropatene s + rotational moulded into lage carboy; and + foamed for structs! foam pallet boxes LDPE i fas good tensile strength an heat resistance, 1 high density takes tra Betr water vapour barir than LDPE, tert sills poor oxygen barrie, Ceti poo an the mater sl ean usually be recognized by ls opaque appearance. ‘Chemict! resistance is good and can be improved by surface treatment, such a hsrnaton or suforation, or by cvearing ‘with higher baer plastics ke mon Tthas only moderate enviroment sees crack resistance, which ‘in cate botles of detergent to factare when stacked. THs property ean be improved by using 2 copelymer HDPE with & Tomer density, reduced ceystalnty ad higher molecule weight “ible 6:2 shows a bresksown ofthe US markets fr HDPE, The Single largest market ie Bowe movlded boues used for mil, ‘eaners shampoo, vgs, moto oll and other consumer prod. ‘oes Injection moulded HDPE i sed for cup and tabs. (Most industrial returnable packaging is made Som HDPE, Including injecdon-moulded erates, totes pallet, drums and sorage containers, There applietons highlight he high strength STHDPE, THIDPE packages can be microwaved, bur he material starts co lose its rigidity a temperatures above 93°C, making ic suitable onl foe foods that donot ge too hot ‘Many resi and fod bage are made fom extruded HDPE fim. eis very strong, a good moisture barrier and is often used to Impart moisture reitance, Extrusion coatings of HDPE ate ‘ed to gle molstore and grease resistance to paper packaging ‘atrialfl = eee ” Packaging Matra ‘ow. pc Co tes soos | Ste anna nmi boi, ae 33 Ina me eae Baron Scand cog Foadpadogg tn 2 29 (Secrets “ar usc cating at rag esienoone Beerdonarestnastopsioingans Tat 33 Teel aon a a a ae ‘aati ovs nas tpt paopmentesae maces” A mtioradsantage of HDPE fie sits high meting pint, a= Jing it suitable for blt-in-he-bag applications. Clarif generally ‘poor and heat sealing although achievable, is more dificult thn To low densiy grades. Pigmented grader of thin fm are fe ‘quenly used wo rae sll bps for we foods Uke seen sh, ‘The diference in the melting points of HDPE and LDPE is exploited in one of the major uses for high density Alm — the liners for breakfestceeal packs. These consist of coracrued film of LDPE and HDPE; he Heat sale sehieved byte inet surface of low density, but it doesnot Fase the enter tough hig ensiy layer. This allows the two surface to be cally pled spartto open. {In some communities, HDPE botes ae colete for resyling 4n the USA, over 250 000 tonnes of recycled HDPE ised ‘annually andthe amount ie expected to increase scaly _Pabofins — plyhyene andplyprogyiene 1 Recscled HDPE can be made into building materials end new ‘packages. When seed to make bots, dhe recycled materia is ten sandwiched between virgin lyers inorder o ovreame he probs of mixed colours, grades and rources. Recycled HDPE ‘Sued, wih LDPE, wo make garbage bags. Low density polyethylene (LDPE) Low density polyetyiene fl is one ofthe mos widely used packaging materiale on che market Tes uses range from thine ge garment bog fl o ners for large water storage tanks. LLDPIE i tough, semitlesible and shock resistant. It sa good berries to water vapour, but many organic vapours and essential ‘is wl prmene epi Ic chem Ine and limon neo ‘ble in solvent at ambient conditions, bat ies susceptible to Its poor ga barser wo oxygen and carbon dow, end where ‘oxidation of «food product i key, commodity LDPE is not sitable, “Tle 6:3 shows a breakdown ofthe US mathew for LDPE, Over 450% ofall LDPE is exuded into ls, whch then converted ico garbage bags, food packaging retail bag, strech and sink ‘mand inurl tage and lines, ee eee ae ee Seon is toa yee 7 a 2 8 = es ooo Seer Noon Ro Gay 990)92 Pachaging Materials LLDPE (and LLDPE) fm can be made by cart o Blown ext sion. Iecaa abo be extruded at» costing onto another material, tnd a signiiane peopordon of LDPE (and LLDPE) is wsed in Imulswajer laminated cr cocxruded seractures where the low dlenscy material vere at beateal mediom, Many lined ‘sructies eso use LDPE for clary and as a water bare, ing ‘ther mates ike ther plastic rfl) o provide gas bari ‘Uses, other than Sm, include injection-moulded consanest, ‘extrusion coatings and ouationel mouldiag. LDPE te used for ‘moulded contrinere where aqueeabiliy ty aeeded, such ‘qveezable condiment container, Some snap-on cap a ase mnade fom LDPE, exploiting ts high elongtion propery. There tre now many diferent grades of LDPE based onthe lng of ‘molecule and their degree of branching ac eros inking. LDPE can sso be foumed to produce cuthioning materiale ‘which ae tough and resistant ro ceep unde load. PE cation ‘is more expensive tan expanded polatjrene, buts eience| ‘valuable for reumble appiestions, Linear low density polyethylene (LLDPE) Lincer low density polyethylene as a diferent strctare fom LEDPE, even though the two compete for many ofthe rame fle ble fl applicadons. LLDPE has an aloe near molecules ssrueture (hence its ame) but ie does include shore branch ‘chains. The LLDPE reins occupy the middle ofthe LDPE den- Sy eange at 0.912-0.928 pom, but their properties ae in most ‘spect spevior to ordinary LDPE. A farther benefits thatthe Same reactas can be used fo produce LLDPE and HDPE. Performance benefits of LLDPE ate higher physica stength in all respects and higher temperature tolerance. Since there x 30 long-chain branching, t hae much greater elongation than LLDPE, LLDPE’: higher tea, tensile, and impact strength, slong ‘with improved resistance to environmental sess cracking allow ‘sronger mater fo be produced wit ess material which Bat Palins — plytnline ond soopromene 93 ‘been expecially important in film markets. alko offers better ‘arenath,durabley and chemical resistance isn LDPE, but fess wansparet. Mealiocene based LLDPE resins offer excllnt clay and sah hit which maker them especially desirable for applications fuch 8 poultry and frozen food packaging. “Typea! uses for LLDPE are for cari bag, strech fms and ‘neary-dty plat sacks. Tecan provide benefits in vitally all polseihyeue applicntins. Table 6.4 shows a breakdown of the [US ashes for LLDPE, eves ‘0 Tomes = Renipetao fn mas oad psn fin eT Sree fn ke Bs Corowa ve ea Yasin as Gina 5 oe, erie oa SZ BD) When introduced, LLDPE was offered et higher price than LLDPE, but since the manufacturing proces lo feed advan- tages tothe producers, increased capacity became available a many replaced old LDPE capacity with LLDPE manufacturing ‘This hat beiped to force peices down. LLDPE was iitilly blended with LDPE as cost opzimization measure, but sore has become valbl, use a single material as grown. LLDPE and LLDPE are often blended with ethylene ving! acetate (VAY to improve tenes, hen-seal o cling properties. Most, Scotch fil, used for unitetion and over-weapping, is made from LLDEB, with EVA added to improve suckinss. EVA Alacuesed rer in Chapter 7L 0 we ce 94 Packaging Marra [New developments —VLDPE and metallocene catalysts Plastce manufectaers have continued the development of the polyediyene family ns they have ered more about the poss Iilet for talloring the molecular atructare by wring different ‘monomers, processes and east. Ranges of very low density (VLDPE) and ultra low density polyethylene (ULDPE), having densities lower than regular LLDPE, have now become evalale.Payicl properties fr these ‘eal danse grades are superior event LLDPE, wih higher ‘longaon, better puncture redetanoe and hot ack (aking them partculsly good for heat sealing through surface contam- Ination), high clarity and eabanced water vapour barrier pesformance:? LDPE resins ace used primary in coextusion or in blends th LDPE, HDPE or LLDPE to take advantage of thei proper: ‘es, Film applications include meet packaging, shri fm and Rozen food pacasiae. ‘Anew generation of poolefins hasbeen developed, using single ‘ite coralst called metallocenes. Applications ae growieg for ‘eve tous plastics, which ate dixingithed by a parcom and highly reproducioleditbution of both ralecula weight and ‘Meallocene catalysts have been found to produce better ‘scength in HDPE, LLDPE, VLDPE and PP aswell: PS and. ‘ther plastics. Moulded ecatainers made from metallocene- ‘based HDPE have twice the impact (rop heighd strength of ‘hore made fiom unmodified HDPE, Making LDPE fli with ‘metallocenes improves dart impact, tear and tensile szeogth Films have better clarity, lower seal ination temperate and presents beter barrier to moisture and exygen.* Metallocene PE filme ere used in laminations as «sealing layer for ligula foods? Paboleins — potion and pobyprpylene 95 ‘With such improved properties, some polyethvtene materials are ‘beginning vo compete in the maskerplace with oter high perfor: ‘mance materials including PVC. Applications inchade mest, poulery and fish packaging which requires low sealing tempera: tures and tate-sensive packaging such as coestraded structures {br cereal and cake liners and eofiee poveh inminstons. kis important to remember that, although polyttyene is com ‘mon material with rate preditaoe properties al peyey= ne isnot created equally. Materials with the sume specified Alensiies can have very diferent propertis depending on the ‘manufscrring process and clays used. As research cnntnes, ‘he properties ofthis important packaging materi especially ts ts barter performance) have been improved ands appietions Ihave been extended, In demanding applications, itis important to be specific egaring the properties noeded in order fo match the material to he itended we Polypropylene (PP) Polypropylene (PP) is another very verealepolylefin, used ‘widely for film and moulded containers, Like PE, ts payne ‘Sruetare can be tained to meee diverse requieipents. Ie hus the lowest density ofall commercially available polymers, which results in high yield. I has excellent chemical resistance and ‘good strength at low cor, Polypropylene's properties are similar to tose of polyethylene, but ls melting point at 165°C is higher than tht of any of the polyelene grades, miking it ical o ee teal direct The igh melding point makes PP astable for microsarable packages {bat not for ue in conventional ovens). Polypropylene provides «good moisture bases, but not avery good ges hari. Like poyetlene, is properties can be tare bythe selection of catalysts, copolymerization, adltves nd mol- oul weight conte96 Packaging Movers Polypropylene i & semi-crstline polymer, andthe degree of crystallinity (and hence its properties) can be coatolled by the ‘manfeciting proces. The order and regularity of the monomer ‘units conf the end properties ofthe product The two ends of the PP molecule are diferent (ee Figure 6.3). Ifthe molecules ae linked head-o-head, the plymer bes ite onde nd does not rsa. Such saci material are not cystll2zdy and so they re soft and tacky and are used in hotmelt adhesives. Ifthe ‘monomer are linked head tonal the polymer is cele ioractc ‘nd seryane. Commecia PP usualy contains about 95% of the toaci form which gies PP its density (ranging fom 0.595 100.920 gjem, ypically 0905 glem?) rooghnes, solvent rest tance siffess ad heat resistance, Stat aay hy Ooo AM gure 63 tn sai polrorsone Polypropylene is avilable a « homopolymer or can be blended With another monomer os a copelymer. Random copolymers have small amounts ofa comonomer, ich a eiglene, at ra ddom itera along the PP chal, These coplymers are telatve= ly clear, have better impac strength and have lower and broader ‘melting points than the PP homopolymer. The lowering ofthe ‘melting pont is proportonal othe randoranes and the emouat ‘ot copolymer. Random copolymers are wed for blow moulding ‘beomse of thei low remperetze roughness, Impact copelymert ‘contain a larger amount of ethylene and are characterized by lower stifies eahanced toughness at low temperatures and a relaivelyopagie appearance, Pooling — payne and pobropsene 97 Substantial modieaton in properties can be achieved by using ‘dives and fillers, Additives can confer resistance to sunlight, Feduce the tendency fo retain state lecric charge, and change ‘he ebetcizne of feton. Fliers sucha talc or ehal (cletum, carbonate) are used to increas slic, improve procesing oF ‘hange the appearance. The use of files usvelly reduces tough ‘es alsesdeiy and increases opacy Merallocene based catalyst technology offers opportunities fe further modicaton, Poypropylene made with metallocene cats Ipet has better mele flow and lower melt temporstores. The sulting fn offers greater elds tnd thinner films, which ean be Scaled at lower temperatures, Physical strength properties ae aso sahanced, Polypropylene i capable of being conrered into the widest range ‘of forms, from ronoflament yarns o pallets. Other applications ‘clue lm (oriented and not-oriented) whic ean be blown oF ‘as, and containers and closures which canbe blow moulded, Injecdon moulded or thermoformed. Table 6.5 shows the major ‘bavkets for PP inthe USA. “Tes US pags es fr P1997 _ Flow noatesceare 7 Creed ins 3 Inger ned il pg Pa Seo role BEDI Sra nde sts Gamat 995) Poypropylone film Film eth largest application, mos of whichis inthe biaially ‘vient form known as OPP (ometimes BOPP). Tere is some ‘on-oriented PP fm used in packaging, primarily for twst-ap cana' fod 38 Pacaging Matera P fim has progressively taken the market previously held by regenerated cellulose im (Cellophane) asthe shin clear over swenpping and fom-il-seal atc for snack foods, cigarettes tnd confetonery. The markt for shes ov alternative mates ‘often refered to a the Cellopp markt. (OPP fl s made by extruding a film and swetching it To orient (uct) the film the tubular bubble is inate or a cas shee is bested and snechancaly stretched bya fretor of 300-400% on tn epparan called a tebter frame, Stretching eiens the long ‘molecules in both she machine and erossmachine diections, Ineresting the toughness and strength “The increase im srength results in avery thin Sim tat i sl ‘strong enough for lumlaation. Te gives OPP Sn the greatest azea Yield of any packaging film. The sm is very stong in tension, bce internal wa strength (ability to propagate a tear that has boen started) is very low. This can bea benefit if eary-tear is needed and a starting notch i provided, ort ean be tation, “causing al ofthe contents of «package to be lost when the fi injce. Orientation als improves PPs grease bate properties and low temperature durability. Te enhances the material's clarity and oes. OPP as ace sti they sparkle and tend to crac audby ‘OPPS high goss, high area cd and abil co be made int very thin fms males i the most economical packaging choice for ‘many consumer goods In eddtion to clgstoue snd sweet wrap~ per, PP fm and PP-base laminations ae widely ured for bags for nack foods and pata and a the greseproof moarre bat sf ner in lal pape: bags for biscuits and pet bods, Its high melting point alo means dhat OPP wil not eat seat without help. The fm ean de coated afer preduction with Feattalable material such as acrylic, which ean simultaneous provide a good favour and aorsa bate or PVC whe {th eveslent gue Duties Alternatively the fn canbe coextraded Bickfes—nbwioimentriomniew with ayers of lower melting point material. thie! opin ete ‘eof shore or cold-sealsaesve (PP atone goo mote bate bt poo bare nye, ght and aroma: Most deeopments ia OPE hee oo inte ea ‘improving is bare propre so in exlting ie laminaton ental. Otter improvement have beef rcs the srfce ‘Sete of ion ane propensy for vate encaton vo that ‘mater a run mere moet info i sea machines, OPP i stylish material which ean appear in diferent guises Te ‘is anlable as an opaque material and an be peated or merle lied, These forms ate growing for special confectionery and snack food application. Another rapidly growing use isa 8 uD ‘trate for abe, especialy foam ade, replaing paper ther ass of rent PP fm afr yas and taping tape ‘Yaers, which are mace from extruded al into tun icbors, canbe woven ne fabric whch se for ey shiping ees ‘Sack woven polyroplene is subst for ft or burl and ‘aly hasan ura ahbitor to protect age that ny be Sore outside. PP srpping tape seal cases ofc pallet loud is being ese in competion with stape made rom neces pujstey, polyamide an fitment pes, PP can also be extruded to make comugited plastic, used in ‘curable sipping containers. Most cocrupatd plastics made fiom PP, exraded in a posie thar resembles a corrugated Rote Doard struct, alzhough some made fot PE and some pes te made by a similar procs to corrugsted Sbreboard, by lami ting two lat sheets to 2 corsgated sheet, Moulded polypropylene Polypropylene is used for blow-movlded bottles and iniection= moakded cap, cubs and bores PP's reputation asa lving hinge ‘ns prompted is use for containers an closure where hinge suLnegal part of the desig,100 Prckaging Matriae ‘Moat plastic threaded, dispensing, aezosl and pump slosure 6 Injetion moulded from PF, as ae most thin-walled tube wed for oghure and butter. Moulded PP is wif enough to not deformn “unde the Toad presented othe thread under tng, but i lex ble enough to allow slight undercuts to be moulded to provide a good closure seal. PPvcape do not need linets Because of the ‘tral’ resience, Fliptop caps expioi it living hinge proper- 'y: Other PP injction-moulded packages include widesmowth ifr, cress, yoghurt cups and cosmetics containers. [PP cn be used to blow mould botes, especial fer sppiatons| involving eagressve prodts tht srt crack othe plgoefine, Carty of FP extrusion biow-moulded botes has ben «Hits tion inthe past, but newer grades have overcome thin problem: ‘The injection-sreteh- blow process for the producon of bodes and jars, developed iniialy for PVC and PET, can alo be used {or prodacing PP containers. The ehenting and tet ofthe ‘hickevalled preform ha he effec of orienting the molecules in ‘he side wal providing enbanced toughness and clvty in the ‘me way a these ae achieved in PP fm ‘Where the material's own modest gas bari properties are equate ingle lye is suitable; but for bores which require 4 higher oxygen barier, it can be provided by either a central ‘cote lye of a high barier polymer which i covnjcted ito the preform, or by coczzusion of the parison (in extrusion Blow ‘moulding o by surface coating. ‘uae suitable for rehestng in amzowave oven However, PP Is ‘rte atlow crperaures and must be bended with other ple ‘ea such a¢ PE whan aed for foaen food packager 7 Vinyl-based polymers “The ving family of pastes consists of polymers based on citer Vinyl oF vinylidene. Te includes. polyvinyl chloride (PVE), pobwiaysdene chloride (PVC), poling] sleatol PVOED, eh Fiene vinyl acetate (EVA), thane vinyl sleohol (EVOH) and obi actate (PVA) PVC slfers fom potethslene in having chlorine atom which replaces one hydrogen stom. Figure 7.1 shows the dference ‘between the molecular repeat units for polyethylene and poling! chive. esate FL ae ‘igure 7. Reet un of poole a PVC “The most important vin, fom a peckaging pat of views ace PVC and PVC. The later eso plays an important role improving the batter properties of other plats. Polyvinyl chloride (PVC) Polysny chloride, sometimes called senply vinyl became pope Tar during the Second World War when fas sed sa subaitute Tor scares natural rubber, PVC i the second largest vee pas tis produced, It uied to make many common household prod- tet rom shower curtains wo credit eards pipes and bung nates fooring tod deioppes. 10102 Packaging Materials Packaging aplictions account for only about 7% of otal PVC sales inthe USA. PVG packages include blow-moulded bots, Diister packaging and meat wrapping films. Table 7.1 shows & breakdown ofthe US mets or PVC. “ae 71 US pean en fe PVC, 197 fim 1 as eerste SGD ‘Shoe at ls Garay 1955) PVG can be made into rigid or eile materi. tis ough and ‘lear (hs sight blue tint and yellows with age), and as good bate properties, Moreore, ti elatiely inexpensive only the pollens aod polystyrene ae cheaper PVC i iia o process ints pare form, being bite and unsta- be. Addie including planers, heat siblizrs,lubecans and ‘nop modes ere equ, Soate properties keen ength fd bares toga and molnte depend onthe formulation, PVC fs wsed in swo main forms for packaging. One isthe ight ‘unpasielzed forin (UPVC). Tt cequies the ise of anionidant Stablizers to reduce he thermal degradation which can occur uring procesing. UPVC js used for transparent gid packaging, soch a5 clear ‘heat for thermoforming, tansparent cartons and extrvsion blow-tsoulded bottles when elo alcohol resistance are needed. PVC botes are used for cooking oll cleaners, chemicals, teletries snd cosmetics, UUPVCie an excellent thermoforming plastic because of ts ably to hold form during the proces and its high impact resstance tnd eluty. One of the most important applicstions is Bister packaging for drug. Vispibavl pone 102 Areas of grow include trays for modied atmosphere packag- ing, food containers (especialy for convenience foods like pre~ puted salads, sandwiches and cooked meats), and transparent fartons. The growing World markt for natural mineral waters, ‘most of which ae currently packed i PVC bots, has also bee 2 growth marker for UPVC, but there hasbeen an scelrating ‘move from this to PET owing to poor environmental peccepion OfPVC and the fing cost of PET. Plastcized PVG, on the other handy is aso, pliable material ‘large proportion of plasticiaing compound, ‘lascized PVC flim have exelent stretch and cing properties. ‘They are used widely for hand-wrapping of esh meat an fh produce, because the water barrier retards weight los wl the permeability to onygem allows meat co keep it ed colour, and fresh produce ro respire slowly, ‘Les plasicized films ate uted for vatisny of wrapping alice tions for consumer products ike toys. Orientation of len wll improve seengih, and itis beatshrinkable, PVG film i so sed Formed! product packaging, and is suitable fr stetlzation by Jnrdicion. eis widely use for amper-eviden chink bands and shrink sleeve lel [PVC isa good barrier wo moisture, gases and odours, but plate ‘iets reduce these properties, Some plasticizers are toxic and thse should not be wed wit ood products Impact resitace it oor, especially at ow temperate I must not be overheated a8 ‘can degrade and release coroive hydrochloric tid “The panied grades of PVC have, in years past been a mater ‘of concer fr food salty sient since residual vinyl corde ‘monomer (VCM) has been found to migrate out ofthe PVG tnd isto wrapped food products. VEM fs been found t0 be carcinogen under vome eondions. In the 1970s, the US. sovernment banned the ute of PVC for liguor bots when i= Packaging Matera lincoveted a rare canoer in PVC workers. The sause was belived to be the vn chloride monomer, traces of which sia be read during terial processing However, grey improved manufacturing techniques have edhced th level of resin! VEM in todays PVC to epic mounts (ander 10 ppb). Since the 1980s, PVC manafectarets have changed both the typer and the amount of plantcis land re now sso using polymeric plasticizers which have less ‘endency to migrate, ‘Although PVC is widely used plastic, thas not been widel ‘eeyled since most of its uses are for durable goose, The i posal of PVG, especialy by incinerstion, has been a mater of fuvzonmental concern, Both PVC and PVEC (which i discussed in the next section) ‘contin chlorine, which has led to» prolonged debate on eheie, environmental acceptability for incineration, Severe Eeropesa ‘unites have banned dei use, Tete «far thatthe pence of chlorine during incineration of west can generate hydrogen ‘blonde gas. Tt ean also, ring incineration, combine Wit Inydroearbonvoastes to produce traces of dioxin Which increta the impact of acid rain ahd pore het rte: Dion prodaction daring paper bleaching as bowie been a concern af desribed culier in Chaps 2, ‘The sits i controversial. The PVC defenders point out that in practice only «small proportion of domestic refuse it nce aed, and when ti cher are other soatce of ehoting,actading ‘od sal n waste and the chemise ae also naturally preset som vegetable materi ike esboages, Modern incincerons ca ‘corporate fae gas scrubbers which remove most of te desta formed. In Japany there ate incinerators that specteally prevent the emission of mich compounds, Much of the ecm does not stad up to seientc analsin and hts been Named onthe sil of scienins ro detect extreme lo, asigifca? amounts, vask- ‘yest dan the amounts present in many natural foods, Vandal polymers 105 cet thetic a iad an on he mit p= Gmc SEPYC and Pv ann may spent the hore See y BE es elope vented oh era peprpsene em tne givin har hey sre ote Sree en Polyvinylidene chloride (VAC) — ie en oe ike neces mec Ghats Rigawel ators nice heated anaes ichmeertnpmene omar ey ett nanan hes mins rea eean be cast or blown into a Bln. PVAG has been extensively the nthe fost of hot watershrinkble begs for poultry, com ‘Rorcalined by WR Grace athe Cryorne system, Othe, lower Cont polymer are now lncressngly being ose fortis Monolayer PVC fm i ahi wassaret (vith «yellowish Sho so song ings ol ho be ed fern apa food bp bot tan ees tril {ert ae compare with competing LLDPE fs PVC is used as the barrier component in numberof coex- fred shect materiale from fms to thermoformable sheets, “The cocrruslon proces: sandwiches a thin PVAC layer which ‘utcient to peovee an exellent bares, between other materi ln Using iin thie way maker economic nense, a the polymer {every expentve, Another benoit of the andvich coexusion i thar PVUC docs act come into direct contact with the metal Girtice of the extrusion die where I could cause corrosion problems106 Packing Matas ‘Maa-layer Sins, usualy coextrusions with polyolefin, ae used to package men, cheese, and other moittore- or gatseitive foods, The ability to withstand the rigours of hotflling and ‘storing make PYEC laminations stable for use a commercially sterlzed packages PVAC tas teen wed as a costing on al forms of packaging for ‘many years Itcan be coated as an aqueous dispersion o applied byonpanic solvent Both methods are ued, expec forth cate Ing of cellophane and oriented polpropriene (OPE) fli. Paper and paperboard canbe coated rth PVEC where moira ese ‘tance, grene resistance, oxygen barrier and water rapour bait ste required PVC hasbeen applied to she ouside of pate botes especially PET and PVC, to inreat thee gre bari peopertie snd male ‘hem suitable for oxygen sensitive liquids such a beer, but these Ibe had technical problems und ave not been comercial sc ‘ceuful. Such coating i usualy achieved bys elpping technique slough spray coating and roller application tecanigues have ls bean demonstrated, Although PVC was the earest specialist baer polymer and now has a amber of competitors i was hola ts potion vey well up ‘othe mid-1980s, especialy since unite ome ofits compton) rovdes an exclnt barre to Both wits vapour a oxen, PVAC hus been subject to some ofthe same ertcsm as PVC. Since the 1980s, the continued pressure on environmental rounds has led re losing marketshare ro alternatives such a3 BVOH and eerie, alcohol (PVOR, ethylene vinyl alcohol JOH and etlone ving acetate GVA Polyvinyl alcohol isthe most commonly used watersoiuble Sm. Ti sed to package dry preducts such as detergent and Virose poles 107 agsicsltorl chemical, which ze added to wate inthe package Iteakes about one minute to dissolve in water, When used with ‘etergent powders, he fim enhances the detergent by suspend ingens cit in soaon. PVOH ie goo gas baie an esis most chemicals. ts sabe ‘tenoderts bat not high humidity conditions Itishea salable Applcsons include dispose bage used i hospital undies feduce the pouiblliy of crore nfecson. Other epecal applicae ‘ons in packaging include uni dse packages fr dificult or haz- trdows material uch as powder dyes or agrochemicals. hylene vinyl alcohol (EVOH) isa copolymer of ethylene and ‘vinyl leh ewar developed to overcome the moisture eeni- ity of BVOH, The motor senivty depends on the propor tone of ethylene and ving alcabol in te copoiymer, the higher the perocntage of tylene, the beer the water este but the ‘worse he barrier Jn EVO, compromise levels cheten, EVO! is best known for being an oustanding berree so grses toch st eaygen, carbon diode nd nitrogen. BVOH i therefore ‘he right choice for many food packaging application, capable of Ising « modified stmosphere aswell s preventing oxida- tion Ie is highly resistant to hpdroesrboss and organic elven, ‘This make good choice for packaging ily foods cable ol, poids and organic solvents eis ao good aroma arse. [EVOH resins were frst commercialized in Jopan in the erly 1970s, and became more widely ued inthe mal9805 when US food producers started using the sein fr alyplasti, squoszable boule “The primary ute for EVOM is fod packaging. Ta most cases it ‘eevee en an oxygen barr ply a cooxtuded o laminated i, Flex line are the largest volume application for BVOH, used {or packing processed and fesh meat, coe, condiments and ‘haske. Depending on the trucare, EVOH-based packages canVi bavd pbs 108 vente hoefied nd scored atmugn tee my beareine |] ereion oe [EVOH strucrures and thei applications. il ‘Since EVOH isl some degre moistare sense, tis wale te) ean be Incorporate in het yer EVOH in also «popular high-barir coating hiding fom gases, q ‘ls, odours and organi olen Irs epplied by spraying, dipping 1 tr rller techniques It used as coating on paperboard —t0 ‘place foil barier for juice bakery and Inundry produc. 0 Eutylen ving acest (EVA) copolymers ofvin! acetate and et lene have simae properties to LDPE. EVA ts often blended rs ‘with LDPE to improve swetch, heat-ealability and cling. Tis fi Used more extensively ia the USA than in Bucope. EVA'S proper l tes depend onthe proportions of ving acerate fo etene inthe from about 3% to 50%. At vay fl eves of about 2036, the materials ike plasticized PVC, soft nd l Cole, continents, sacs, aw. ‘ie lay ay rece {nd hertwating performance } [EVA is coexaruded with other materials 0 improve strength, fieeee-crack resitance and est-ealabiiy. Teean be extrusion i laminated to metalized polyerter for bapin-box constructions Shee Fewer Eden sb cosines (VON Tay Ena ky Rey (19897 9358 om contro Tet itd cam{| u = = 0 Pachaging Metros {or lquid. Pema meat ets are vacuum packed in &coestusion (Of EVA and PVEC. [EVA copolymers area primary component ofhot il adhesive, Polyvinyl acetate (PVA) is elso commonly used vinyl-based adhesive for paper. These edhesives are further drcuseed in Shopter 1, 8 Styrenic plastics Polystyrene is the most common styrenic plastic wed for package Jing, but there are x number of other copolymer plastic base on styrene, including aerylonrle butadiene eyrene (ABS), styrene scrylonite (SAN) and styrene butadiene (SB). Styrene can be ‘opolymerized with other monomers in order to obtain wide range of properties. “The syrene monomer is quite diferent Som the olefin type, 8st fn based on an aromatic molecule (oae containing the Genaene ‘ing in itstectre. Te forms fm chant reset ostlon, ld ‘nga sti brtde mace. Styrenes are able wo cyst and sore igh ansparent. Polystyrene (PS) Plysyrene resin is one ofthe most vesatil, exsil fabricated sand cost effective plastics. Ie can be moulded, extruded and ‘oamed. cis widely wed 0 make study but disposable dtiware, jewel bores feed way, closures and eathioning. Table 8.1 shows 1 bretkown ofthe US mares for PS In some communities where economics or legislation is fSayournble, PS packaging, especialy foamed PS, i recycled, When incinerated, PS, like PVC, causes unacceptable gaseous emissions and special scrubber equipments sauce, “Two pes of polystyrene are avilable: general purpose and high impact. mma Pachaing Material ie es SSanor a si ‘eines oH ieee fH cose 3 8 Boorman & # Eamon ae 3% Bom n of E oes Sa ee age ig ee i = a Saas ‘Soc: Mad ns Garay 958) Genoval purpose polystyrene General purpose poiyszyrene ia gost, highly ransparent,non= crystalline pljmer (deapite is frequently teed trae, cystal polystyrene, which refers to its clarity and hardness rather than ft scracture) Ts surface smoot and shiny. Iehat a density of 1.05 glem? and softens t about 95°C. “General purpose PS is brite, which has restricted is use in packaging mainly to thick, cet, injetion-moulded containers bike jewel boxes used for badvare, suo eeper ad CDs 09, ‘cosmetic, ad (the name mpi jewelery I is a poor wate vapour and ges barcior with low hest-sel strength. Blow-moulded bole are ed for teleurn powder, [Non-packsping epplications include dirpoesble medical devices, clery and danking cups Syren patie ua ‘Moat PS research has entre on improving the physical peor ‘mance to reduce briteness. Metallocene technology could in the future play ole i improving PS by increasing is strength tne decrasing brtdeness General purpose PS can be extruded a ler film, but his slo tends to be brite (hs a characteristic metals sousd when ‘usted and has found only smal applications in packaging. An ‘ample is the wrapping of fowers and certain fresh produce Such as lee where che fl’ high permeability (reacebii) help to zeavier wt by convollag moisture los ‘Two Kinds of PS foam are made fom the general purpose grade. Foaming reduces th britlenes of PS and exptalzes on ts iid iy. PS foam ie the mos widely used packaging foam, used for ‘nhioning insulating and vod filing. In recent years i i Feceived increased competition for ‘hes eppicetione fom Pi ‘babble fm, moulded palp and wong ar acs. Blowing agente, which expand when hestes, ae easy to incor porate Into PS. Whea heated the expanding gus gives a cell Fructoe to the PS. The orginal fluorocarbon blowing agen, Which were controversially inked tothe depletion of she earths zone layer, have been replaced with hdrocarbons. Buraded polyatyrone foam is made in a sheet which can then be easy thermoformed. This material has good cushioning and Insulating properties, and is used for meavvegetable ays ‘Sarton fst containers anda a protective abel material fr ‘dass ote. _Bepanded polytyene (BPS) foam is moulded from preespande ‘od beads EPS is one ofthe mors common cushioning raters, ‘cd eo protect agile product ike appliances and electronics. Ie J moulded into inslared boxe for fesh fh Te also moulded ‘to nll shapes tobe used ss a dunnage material or locating fitment, including “loose fl o fll vols in packages and add protection to edges and comets.awa oe es cere t us Pecaging Maver Sane pats 4s ‘Bnxialy oriented poleyrene Hl sels es brite than gener purpose PS. Its clear, sparkling sect that ean be thermo~ forme ino clear, tough fens ke biter packaging and ays for ‘Confectionery, sla, lect and condiment I competes wih PVC and PET and akhough els more expensive, thas «higher yield beese oft lower deny. COsiented PS has a narrow thermofiem temperetare range (110-125°C), narrower than PVG can tolerate High mechanical pressures ae tse in the thermoforming operation fo iinet endency fo erik a fear tr malting point. Heat rexisance of PS ins renviting factor, end efforts to make OPS more hest sssisan continue, amg fer the microwave meals matte, High impact polystyrene (HIPS) High impact polystyrene has a small amount of rubberiike polybutadiene or rene butadiene blended in to overcome the brittleness problem of general purpose PS. The material is ‘oogher, but ess clea, usally tanducent or opaque. “Thermoform HIPS i se inthe packaging f foods but mast De processed with cae so avoid tnie problems. Some applic ‘ons nelle cups and cubs for refrigerated dary products, fingle-servng cups lid plates and bows Tes also used in mle lager extrusions which can be termotorined to make containers for asepuic food packaging. ‘A recent development is the addition of polyphenylene oxide (PPO) to BIPS, which hasbeen fund vo improve hea resistance, ‘oughness snd suengih PSIPPO packages are microwasabe Styrene copolymers — ABS, SAN and SB “Tough copolymers of styrene are avilable for packaging appl- ations: One is ABS (acrylonsrie butadiene styrene), & (ugh Ghermoformable material. It is x copolymer of serene and accyoniie with the butadiene Srey dapersed and tapped ‘thin the moles ate me By varying the proportions ofthe thos components, & wide ange of properties can be obtained. ABS polymere ca have sgvod chemical resistance, are tough and hasd, resistant to scuffing and staining and have very good impact, tase nd fee “engi ABS canbe eller wanucet or opus the base tsa ‘has a yellowish colour. aan ADS is caslyhermoformed and moulded, Major ue ates ae for ‘consumer durables ike refiigertor door panels und astemobile Dts Is high impact swength eles wef fr tore bowes and teas expecially arg ones, Because ih a low tendency to wut “There are grades whieh ere used for pckaging, munya chin thermofoemed margarine eb or tens and conmetcs packaging. However compared with competing packaging mater, te oat ‘Of ABS i high or such consumer packaging applications. Soyene acryonitie (SAN) copolymer is another material which ‘san have packaging applciionsy he largest of which sa #com= ‘nen in he mance of ABS ssn, ‘SAN is clear rig and gosy nd tis offered as an alternative 19 |ABS, PVC aad OPS for cotmetics packaging — bottles, over ‘aps, closures and spray nozales — where clay san important feature. Ts characterise are deerained by he rato of styrene to acrsioniile @equendl 3:1). Te is nota pertculry good gas baatrit, but this ean be improved by inerensng the wcrlonite ‘Sorene butadiene copolymer (SBC) isn reasonably tough, tans parent material with slow dene. Tis more expensive than Dololefins, bus less cosy than polytyrene, when competing for similar applications. Drewbacke inchade a relatively high peer6 Packaging Matra ‘SBC is fequently blended with other compatible ene like PS and PP to enhance ther performance, coneibating sifaess, hardness, toughness, tength sod high optical propeste, DPSISBC blends are uted in single-service fd packaging, bots, blister pack, oveeape and fm. SBC i aleo Blended with PS form HIPS (see abo). ‘SBC can be converted by al processing routes into containers, sheet lm and so on. Ie ean be made into bottles, Sim sad ‘hermoformed containers for food and medical prodvets. [eis widely uted in medical packaging becnse ican Be steized by ‘oth gamma Sadiaion and ethene oxise ‘SRC bloven fl is highly permesble and is used for wrapping fresh vegetables. Injecton-moulded containers can have a Meable Inge, similar to thove mae from PD Tels better known by ite swadename Krein and is more widely used inthe USA then ie Europe 9 Polyesters Polysters are the fastest growing group of plastics used in packe ging, primarily because oftheir widespread use ln large boas fr euibonated soft drinks, “The trm pelyster ever a wide range of materia The east, ‘ue wat ava ete flr; clothing, carpets and soft drinks bottles fre all mde from PET. Boat hulls and Aohing rods are made from glas-reinforce thermoset polyester commony called fre il. Polesters ate the product of reacaion becveen sore Sid ane am organic base, andi i the thermoplasie pes which te of interest for packaging Polyethylene terephthalate (PET) “The primary packaging ute for polyeter is ex polyethylene ‘erepihalat. PET i nee ed ashigh cari. eis rong, tough sds ie the moulded foe, su I na relatively good an barrier an olerate fue high temper. stares, These properses ean be improved by arlening, coating oF ‘opalymeriing er one ofthe more expensive pasties and ‘ued hen fs superoe properties ae needed There sno eesuic- tion on is use for food contact, and most of applications are fer food. 1s sed for rig containers ike bots, ra blister and jars ‘sella high pefortmance fle, The pemoary applications are ‘shown in Table 9.1 a7i 0 Probes 9 ue Packaging Mavis “eb US petging he PET, 190 ere "0 tones = Seine boies =e Emer movie oes he Ger et 38 eee eg een SHRED ‘Sow Madey Pie Uouary 1988) PET bottle ‘The highest usages in bees wsed for soft drinks and water. PET has seplaced PVC ina numberof sppiatons fr envionment eanons and where ea saprime concen. The se of PET rgd bouts expanded inthe 1970s arte ele ofa satcy by Coca (Cola to erent the ales of soft drinks, Larger containers wert ested, but problems wih the weight and safety of large gies bo tes stimulated the search for alternative materials A filed PET ‘vodizebotie weighs 24% les than asim gles te ‘Atthat sme, the exelens physical performance of polyesters wis well known and the barier properties, although only modest, ‘were fatto be acceptable for drinks with a short shelf Performance was farther improved by the newly inreduced bias. Int orientation effet of sere blow technology for making plat tie bottles, which had initally been demoasuated with PYG. ‘Moreover, the sali ofthe matesal was increasing oming 0 ‘decreas ints demand ia wae applissions. ‘Since botdes for carboneted sft drinks have to withstand high Inernal pressures (upto 4 atmospheres oF 60 i"), at bases faze not possible because they would blow ouswards Therere, the fret generation of PET sof drinks bores had hemispherical ‘bes which were made stable by the addition ofa separate base cap. Laer developments axing amie dome’ design witstnd ‘he interaa pressure while stl providing reasonably sable ba ‘Loss of carbon dioxide chrough the Bote walls does occur but the rte has been found 1 be acceptable to retailers end mand- fururers. Trials to reduce this by costing the ousie surface ‘with PVaC copolymer barrier resin met with mixed results; ‘una eaces of eatbon dioxide permesting through the PET ‘became blocked by the barrier Inyer and concentated in the form of small bubbles or blisters on the surface. Although beter coating technigues can eliminate thie problem, it wae deter ined that there wat no nee for auch a coating, ence iis now ‘widely accepted that a soft drink’ carbonation level ca fall by up to 13% over 3 90 day period, wel within the sel@ife expabiiy of PET. PET was frst wied for are sizes (1-2 lees) since this range ‘was most economical and performance-effecve, Smale botes took longer to be adopted, since the carbon dioxide barir i ancton of surface aes, smal bottles have a higher rat of car- ‘bon diode oss and comings ate required. PET Is now accepted ‘onboth economic and performance grounds for bots ae ema 250 ‘Wine, spa wares (pia and carbonated) and toiletries are now sold jn PRT bowles, One aspect whics nally Iited the use of PET for che ultra innt-enstive pure mineral waters was the Inevitable prsenee of minute wates of aeztaldzhyae in botlie walls. The organoleptic (ast) effects ofthese minute traces are heightened bythe presence of erbon dioxide. Tis problem has now been virtually eliminated by improved manufacturing tech- rigues which reduce the quantky of acetaldehyde t0 tiny motte. Any such residual traces are driven off inthe heated ‘tretch-blow procesing sage. Now een cembonsed spa waters se satisfactorily peckaged in PET. PET bottles are usd fr alesholic beverages, fom 50 ml aitine liquor mini-towes co 30 lite party packs. Botles fr edible oil sre increasingly being made from PET eather than PVC. It ‘ess weak ads, basts and mest solvents\ I w0 Packaging Materia PET is also uted in some countries for ber bores, but here the critical nee isto preven the ingress of exygen rather than jt the los of carbon dioxide. Oxygen causes beer co go sale. In order reduce histo an acceptable degre, PVC bare resins have been applied as an enteral coating Alternative, a coext Son technique sued to incorporate barrier component sich [EVOH or MXD-6 smorphows nylon’. The ler approach the ‘more suceesfl, bu is more expensive. Since the md-1990s the Use of PETIPEN blends, ores ll PEN (pojehylene napa lene dicaboxylt, has been propose for ber bots, since dese cn be designed to be returnable nd ths jst tei high cor PET widesmouth jars ae use fr foods, especially fr dried prod ‘ats and thor which are not hoe filed. Some very high quality ‘hickealled bores and jars made frome PET are used in Japan for cosmetics and ween Many diferent effects — ch as clot, ‘rkmati cr gas faeting pencesent and frosted fishes — are ‘Schienbie, These hnry conniners are very expeive and Rave ‘otbeen adopted onthe sre scale outside Japan, ‘Anormal PET streich-moulded bottle cannot be filled witha hoe product. Above 60°C it wil digort or shrink since the second roctsting sage leaves the container with «hee reteacon mem ‘ry The most erieal area is he neck since irmust A he intend ‘closure scart ‘Various methods have been used to enprove heat stability. Most lnvolve increasing the materia’ crystalinity with het. A dual ‘ould method feats and shrinks « moulded bot, and then blows it ina second mould. Alternatively, dhe Bote can be Bel {nthe mould for long enough to relieve the srestes, There are also methods ro selectively stabiiae the erie neck ee, One fo subject che neck zone toa farther heat treatment which er" tales the polynes (CPET). Alternatively, a second igh mele- Ing point ein (ike polycarbonate or polynryat) i sed inthe ‘nek, o the neck thickness can be incresed. Grades of PET with ‘igher temperature tolerance sre being developed, and hot, temperatures to 85°C and above are nom possible. Popes a “The profile of che bot can alo be modified to accommodate ‘gher temperature, as demonstrated inthe unit portion package Iago js ac pscrves which ee hor fled using standard PET. traces, Despite the prodvt temperature being higher than show Evtolerable the mats of the smal old jar as» proportion of te ‘rept ofa filed cols he product suiiendy during ling, ‘Besides heat sestance problems, hotfiled PET bots ar so ‘eptbe to racuum colape when te product cools. To reduce the eflect of the ditordon, bot-led FET bots are moulded ‘oh vacaun pane designed to dstibute the distortion wnifors- 1) around she bode Bowes mde from PET ae the most highly cyte ofl plastic Containers Over 30% of PET bots ia the USA are reeyed, Dpeimariy owing «© deposit systems. in “boule bil” sates, Recleimed PET isin great demand for applicasons euch a ‘breil, eles, carpet thermaorms, non-food concsiness and ‘trapping. PET can also be depoiymerized (mechanolyei) to ‘ever the polymer tothe orginal monomers, which can ther be Fepolymecaed, Market testing of a PET “eat? with a metal top fated nthe USA and many cher counties i lege par owing. Cioizonmnental presares tha favour single mater packages (or ‘eyeing Tis pack remaias in Tinted use in Europe, PET films Biscay oriented PET i thin, high performance fi Te was tizinally developed for scoring tapes and is used mostly in low suges,typialy 12m PET sim has exceptional eile strength i dimensionally stable, Clear and suff Team good aroma bares, but ks moisture and ‘re bate properties re only moderate It's not heat sealable, but it cam be costed or solvent-saled. Tes excellent thermal properes, making it good choice or ood which is led hot or cooked inthe package. Ie tlertes] core Re Pchasing Motrials temperatures ranging from ~10 19 150°C foe several hours and can withstand even higher temperstares for 4 short period of PET fim is often coated with PE, which provider sealbiity, oF PVC, wich improves moisture baer properties, Sach materie aly are used in boiLin-bag applications, packaging processed meats such as seuseges, and a liding film for sealed teays hich can be heated in-e microwave or conventional oven “Thicker, reverseprated PET fm is commonly ove inte oe layer of molilayr stand-up pouches prove thermal #abiity dering seating As well as providing high strength for + number of muli-ayer ‘seuctures, PET fm is an idea! substrate forthe varus met lization process. When coated witht minutely this layer Cone nilliomth of an ines) of aleminiom, vapocied under high ‘acum conditions the mygen barie improves by = factor of 100-1000, depending on the quality of the metalizing and che thickness of metal deposited. Mealisng alo produces dere ‘ie shiny surface, Metalzed PET is used for cle brick packs, begi-boxes for tiqidprodacs and bags fr seack foods ik post crip whic equi thin but excellent oxygen barrier, Such snc fads have ‘tremely high sutece area and high ft content. They ate therefore parcuarlysuscepabe wo edition rancid Thi mechanisms ‘accelerated by lg, vo the opacity provided by metzson fe 2 Second important benef. The mor comoa bag ben material ‘a thre-py laminate of EVAVmetalized PETBVA, Anothe re foc vacuum metalized PET is for susceptor film ose i mico- swavable packages to impare crispness fo food. The metalizton process dues! in more deal in Chapter 13. PET slr seas to print Te is vee a abe teil inchoing metalized lbs Ie alto ured at Hologeen subsea ialiy ‘hosen as & material for credit car with holographic security Isbeie Pass a [PET fim is leo used in bigh performance retort pouch truce tures in combination with aluminiim foil end HDDE oe PP, Retort pouches are like Mesible cans, in which food i cooked ster packing. This materia), which ean withstand bet the ther- ‘ual and physical stress of poste retrtg i used extensively in Jepan and some parts of Bsrope, Retort paiches have never ben very popuae i the USA and the UK demi high expecta tons during the 19705 similar structure i, however, ed for some medical packaging apllstions. PET fm rele expensive, but here are sings a processing ‘hough form fil'seal machines bese they ea be ran high speeds without the dstordon which occurs with other materials Thermoformed PET —APET and CPET Amorphous PET (APBT) canbe extruded into sheer and used for thermoforming applications. The resulting materia i cae dered for high gloss and is more expensive than oer thermo formable places. Medial devices are often packaged in APET. thernoforms ‘The same grades of APET are nding spplistions forthe peo= Auction of transparent cartons Sheet materi eerste, dia cat and sde-smed by adhesion or heat. The packs afer an airse= tive appearance fr clerics, exiles and small household tes In most such spplicnons, APET compere dircty with PVC — fiom which tis visually indstinguishable — and with ect PP = which although more cloudy is making some inroeds into the ‘wansparent eaten market Aldough PET is more expensive than PVC or PP ithas a faster cyle tine in thermoforming is en- ‘10 use inplant scrap since thermal degradation fe lst of & problem, and no sabia adaves sre needed ally crystallized PET (CPET) ists subject ro deformation ‘under ses, epecaly at igh empertores, bat rite st cold emperatues, Te used to make thermoformed dusl-ovensbiems Packaging Matra ‘toys. This isa high growth market, elated tothe growth in microwave oven ownership, which is acdvely pursued by rete and food manufacturers who provide ready-prepared (rozen oF fetuigerated) meats. In some cast, duslovenabe ays have a APETICPET struceure, with the CPET providing rigidity and the APET providing low-temperstare impact sent CPET is manufactured wsing «traditional ehermoforming process fr thick shee bt the try remain inthe forming sald fora few eeconds to achieve eration, The elle vibe in thatthe eansparent tay tiene opaque white. CPE sheets can also be extruded in» fosmed form resulng ina lghter-weisht tray which hasbeen used for baked goods. CPBT trays can tle "He emperatures up to about 220°C. Paradoxically, if only microwave oven tolerance were needed, PET would not be considered since thermoformed PP cays ae less expensine and are quite capable of withstanding the 100-110°C temperatures generated by microwave ovens However, provide customers with maximum convenense and ‘exbiliy food manufactures recognize hats way stable for both microwave and conventional evens to be pefered, ‘igh performance polyesters — PCTA, PETG and PEN ‘The complex chemistry involved in the synthesis ofthe polyester group of panics allows for the posalblty of aay farther vari ‘ons offeting particularly atzactive benef ‘Ben higher temperature grades of PET are now swilabe, PCTA, copolyeser (eelohexanedimethanal aad terephthalic acid Copolymer modified with anther acd) i a etal matetal With avery high meting pint used for dal-oven rg. Fecan be toyed with other plastics or fled with glass fibres or mice meet a variety of performance criteria, PETG copolyester Is a glycolmodifed polyester. In sheet form, is melt temperatures range from 230 Io 250°C. It ean be Pests Bs ‘extrusia blow moulded nto clear botles, etruded ino fl and ‘hes for thermoforming, or injecion moulded. Both PETG and PCTA ate serizable by both ethylene exide and gamma eas. PETG is injection moulded into thick-walled jars for cosmetics, both cese aad trantcent, whieh look and fee ike glass and fave croton resisance to land aromas Tecan alo be used to sake packages fo fo and detergent swell a trays formed fea devices, Te materi sof igh pss and clarity and ha very good procesing character. Tes easy to prin with high qual= ‘y erpiies, including meralie fll wansfer. Ieeompetes directly tite PVC, and although PET has superior visual appearansy itis sigalcanly more expensive. Improvements in sandard PET Sod PEN make thie mae of diminishing interest. PEN (polyetivlene napalenedicrboxylats) has superior bar- Fier properties ultraviolet resistance and temperature stability, Thaking particularly sub for hot-il fod applications Rigid PEN bots are ratable for use In terurnablerefillableapplew tions because they are her essant and can be resteiized for ‘Competed with PET, PEN provides approximately fv ies the barrier for carbon dioxide, onygen and water vapour. Tei ‘tuonger than PET end UV resistant. Its high-temperature per~ formance beter, which enables products tbe hot filed with foureidesall distortion, which ia problem for PET. PEN can be moulded nd PEN hotles can be used for foods a8 vel ay secholic and carbonated beverages. PEN bottles are beginning tobe uted for bees, « demanding application which requires 2 good oxygen and uiravoet base, PEN can be blended with PET, and PET/PEN copolymers fan be produced, Such combinations optimize the high cost DEN material and ste expected to grow in food packaging applcesons0 oo 0 om co 25 Packaging Matriae PEN fim ae stifir than PET, simultaneouly providing thin= ‘ner material witha better barir. Appictions ince sten-p pouches, modified atmesphere and home meal replacement packaging. Pure PEN can be eaiy separated ftom cher plastics because t fhooresces, which wil facare ecyling iit becomes widely wed [Reeylingis an important opin fr sch «high cost mei. ‘The fest PEN applications were in Japan tnd South America, but Uhre i acive interest worldwide for hi high performance las= tic. Becaute ofits current high cost i has been ured only for ood packages where high bares ot high temperstre ute it essential, Homer the price falling owing to the use of new, less expensive base material and increased proction capacity PEN is expected wo epproach cost competitiveness with lower peeformance plats. ‘The potential for new classes of polyester, as exemplified bythe PEN material, is such that they could offer the possiblity of being the ultimate plastics They ate inert, require no separste sitive; ate fully feyelabe and can either Tach the pefor= ‘mance of tadiional materiss or atleast provide an adequate level of psformance fr moder fod dstbaton. 10 Nylon (polyamide) ‘The group of polyamide, or nylon (lormerty « DuPont teade- ‘name, although twas deseloped inthe UK), comprises a clas of chemical developed in the 1940s. Like polyesters they were ‘sed nil for textes. A few of here have found packaging pplicnions, hough dey are uly fr bighly specie applica. "ons where cei igh gas baie and strength properties meric the expense, [Nvlon type 6 and subtype 6.6 are the most important or packag- Jing, Polyamide chemistry is comple, anda system has been developed for naming he ypes bated on the numberof carbon toms in the orignal monomer, which represents the sizeof the Feet group in the long chan plymner.Nylon-6 has sx carbon ‘toms, and tylon-6.6 a subyype of aylon-6. ‘The properties of aylon which are of greater significance for psckaging applications are its coughners and sutcngth over ‘broad temperature range, puncture resistance grease fxstancey ‘sistance to stress cracking, and barre gates oil fts and absorbs water and bas relavely poor water ‘vapour transmission propersies, Bur this can be improved by {pplying « PVAC coating. Nylon can be castor blown into Sm, Slow moulded or theemo- formed. Nylon is expensive and ir offen ured in coestaded structures with other plastics. Blot-mouided bottles for har toshold chemicals, like tolletes and household clesner, ae ‘ade by using nylon as an outer ayer in extrsion blow moved plastic bores, which provides a highly erste glory surface. ‘This may also be pigmented to pve a coloured layer overs more inexpensive commodiy plate sch as HDPE, a28 Packaging Materials Nylon film ‘Much ofthe mon in packaging i sed in the form of mulayer films produced ether by adhesive Inmination, when the oriented form may be used, ora coexrasions, usally with polyecylene ‘or polypropylene When coestruded wih polyolefin, slong ae ‘he mel voces are eccurstely matched dhe materiale donot equi an intermediate le layer. Very thin oriented nylon fn ‘az be used as a component of high performance laminates, often ‘ompeting with PET. Nylon i els a good film for metallization since its ow thickness allows long runs inthe sealed vacuum, ‘amber, giving good production economic. [Nylon hae «high meting point and the film is ifcue ro heat ‘eal, though wl, corona tested and given enough het ond pressure. Alternatively, it can be coertraded of laminated with ‘anly hau selabe PEL ‘Nomis ane ofthe few lm material (PET is noche) which in its non-shrinkable form can be used at bigh temperatures, ‘Therefore, icis used for cookin bags and vacuum packages for processed meats, For certain applications such as ham and ‘Special eausnges the product may be cooked by the manufacturer in the nylon based package. Nylon film's coughness is wsefal ‘when vacuum packaging is used ifthe produce contains sharp Particles or bone its puncture resistance is ao «major benef. For exaraple nylen is used for packaging hypodermte syringes sand military spate pat ‘when tsps barver properties ar go requted, aylon i cost lfectire flution; but if shee are not needed, there ate less ‘expensive alternative Ike HDPE. Nylon js coestreded and laminated to ocr Slim substrates, Applications for coextuded PETaylon/PE fms include bacon, chess, mest aeaty and lly foods, coffe, gs-Dushed products Nylon ie laminated to alumni fol to make a retore pouch laminate or ic can be metalized to improve the bari and #0 Noon (obama) ne Imqpare afte look. The metalized materiale used in insti ona coffee pouches, metallized balloons and (ia combination ‘with EVOH and LLDPE) bag-in-box applications, ‘The high strength and voughness of njon fm can be improved by orientation, ich alo improves barier properties andreas ‘rick rerintnce, Compared with oriented PET fm, oriented nylon is better gas barrie, softer and more puncture resistant, although PET i more eg and a better moisture arse. ‘The most populasorented nylon film i produced from nylon-6 poljner and canbe either cst exrded a sheet and then a= fnted, oF extrude in the Japanese ‘double bubble” method in ‘which s second, cooler indation sage takes place oa s tubular fraion ine “The proper ofthe ial mera are very much infuenced by he degree of erystalinity, which in turn relates tothe cooking process. Rapid quenching in the easing process produces an ‘Snorphows type of material whereas low cooling encourages the ‘more regular eryaline sate, Thermofoemabity andthe degree ‘of ransparcney areas infuenced by ceystanity. Since the rte ‘of cooling cannot be we precisely conrlled in the tubular blw= ing process, tabular extrusion usually produces fl with lower ‘mansparency end glss. 1 thermoforming, nylon can be highly elongated in deep draw ‘oulds end rset stress cracking daring moulding. Nplos-6 fRequently coexerided with polyolefins or used a4 couting for paperboard paper and flo enbance thei properties, "Nylon is one ofthe most expensive packaging ms. "The largest sources of oriented ilo fms ae aly the USA, Denmark ad Japan. ‘Other specat forms of nylon are finding packaging applica- tions by viewe of their gas barier properties. Amorphous polyamide (AMPA) canbe dispersed within larger proportion0 oc I i= 20 Packaging Materials st ree ogres ee eee Paes eee eee eee Amorphous polyamides are also miscible with copolyamiées, poljester and EVA, They improve oxygen and aroma barser and technical properties in coexrurons ured for bottle, tubes, thermolormed srrates and savage cangs® ‘Although moat polyamides have e matked sensitivity wo water, ‘AMPA i uid actually to improve is oxygen bavier peeformance achighe elas numites. Tn his respect ics exacy the oppo She to EVOH, one of vlan the high tree market. Another polyamide development ie MXD-6, high barre nylon terial based on metaxjenediamine xylene copelymer. Ths it ‘ted in Japan a the barrier core layer ofa three-layer PET bowie for wine and beer. Some new polyamides Gemirrystalline a well ft atnorphove) have alo Been offered tea sandwiched Sarier layer in reflabe polyearbonste bots. 11 Cellophane (regenerated cellulose film) Tels over 100 years since cellophane orginally a DuPont tre- ‘natn for regenerared cebulose Si, or RCE) we patented i the ‘UK. The name combines the words celloee tnd dhophene, the [French word for wansparent.Iewar avery expensive cansperent Sm avalsle in Beawtiflsher colour, weed for the packaging of kixey items. Inthe 19308 the technology was developed for ‘coating with moistare protective eee ‘For 40-50 years the material enjoyed «steady growth in packag- ‘ng arpicaons. As the ume, twat the only auch leat portaping rateral. However, ence oriened polypropylene fm bectme svllble, its properties so closely matched celloplane tht it "pid beg tobe adopted as «lover-cort substi, So closely fe the to material densified today that they ae equentiy refered ro joint a comprising the Callopp marke Calophane iin estence now a niche materia catering o speciale sty markets where ts characteristics sre unique. It maintains ¢ “dead fold” (keep ts shape after folding) which & important for ssiscveap appliesions lke hard eandy wrapping. Iti ety ‘eas, which makes packs easy to open tis ety ot ac stl, has high evel of gloss, resist high eempersture, and high moisture permeability can be an advantage for products like cheese and pastry which eequire protection sguint bactecal arowth, When coated, cellophane i good Cate to meistare sd oapgsn. Coatings so enable the material abe heat sealed ‘Worldwide consumption for 1995 was entimated tobe 1.45 mil Hon fons withthe few large producers locsted in the USA ar132 Pashaging Materia Calephane ie “Mexico, Burope, Russia, China and Japan? The primary markets {or ceopane ee for confeesionery twitwrap, bods like pasties, ‘and soft cheese, pharmaceuticals and healtheare products. The ‘overall ratio of ellophane to OPP in Europe generally thought {be about 1:6 on weight ass and about 1:10 icalelated by tea since cellophane at 1.3 glen i considerably denser than ‘OPP 20.905 pew CCtiophane i considered a polymeric material since it comprises long chin molecules of repeat unt, bat it snot = thermoplastic ‘because it is nether produced by @ melt phase nor capable of ‘being shaped by het. “The materi is produced fem high purity wood pulp (encaly= ‘sis especialy sltable by dissolving the cellulose resin cat- ‘bon cisuiphie, then adding sodium hydroxide which converts the soon into scone a dasolved wood pulp. The gelatinous ‘moter is "ipened? for & few days and then removed through & narrow slic orifice onto 4 eustingdruin on which it then pases ‘through forter stabilizing liquids, mainly sulpharie acid. This regenerates the lm by coagulating the vsconesolsion. After Datsing through various washing bats, the material is pari ‘led, to make i les betde and more uable ar» packaging material, by adding ethylene glyeol or propylene glycol (onl the later maria is allowed for this purpose inthe USA). ‘At this stage the materia is exremely moisture sensitive and forthe vast major of applications is then costed using ekher nitootiloe or PVGC barra ucgutr, the aes provide ing much beter performance. As a result there ar far eimary ‘rede ofcellophane (ith minor delasions in diferent couse) hin, wncoated Sim MS = moisureproofnieoclolose-conte fm MXDT = coated with PVAC on one side [MBOCT = coated with PVAC on to sides “The MAGKT material the mort important and the highest pevforming arade. I is further subdivided by reference 1 the rethod ted for coating the PVAC layer. MKXT/A bs an [gucous dapesion coming and MXSCTIS ha a solvent disper ‘Son coating. The A grade har a aghly bever bait. Unite ‘mow other feb packaging fins, cellophane is specified not by thickness bur by gauge (p10!) ranging from 260 <0 600 g/l0 m ‘Aihough cellophane has lost many of its traditional over~ ‘wrapping epplictions to OPP, i consinues to be used asa lm tute in combination with LDPE, BOPP PVC andlor metalized polyester. Such laminates are ust primarly to package pretzls, Popcorn chips, aus, meats and cheeses. Cellophane i verastile materia: it canbe dyed in arange of uracive colouce and ian excelent eubatate forthe metliza- tion proces, Combining thee wo techniques produces some dazaling visual effets “The environmental effects of elophane ate a manr of debate, 1. js produce fom fenewablenatorl resources and the uncoated form is biodegradable, However, high quality wood is used ‘which set renewable’ than other woods and most applications Ure costed, nd so they biodegrade very slowly. Tt has been demonstrated that cellophane can be made from other ceiosic fed material ineluding tras, but tis is more difcalt and tapensive Ifthe material could be produced economealy fom cenvered wartepaper sures, and the nature ofthe volatile and liquid waste products atsoiated with ts manufactare could be made more sccepable, it could ly claim to being one of the soe gree’ of packaging materials. Ceitulose acetate Catalase acetate is one ofthe derivatives of cellulose which has ‘een eae very eaty form of plas. Ic has some excellent oo14 Packaging Materials properties including very high transparency and gloss. Is easly Converted into cartons, ments and window patehes by thermo orming, adhesives and solvent welding, Porter derivatives, cellulose acetate propionate and celalose acetate buryate have generally similar propersies but greatly Improved roughnes. Cetnlose acetates have been replied in most major applications by other plastic materials Transparent cartons are produce more ad more fom high lary exlendered PVC, especial with the advent of beter cessing echnigues which overcome PVC. tendency to whiten and fectre atthe creases os well a fom [APET sheet and polypropylene. The we of cellulose acetate ‘hin fl for winow patches ln cartons and envelope has come ‘under threat Som oriented polystyrene fen whichis easier #2 ‘anufueture and i more penta supply. 12 Plastics’ barrier properties and performance “The preceding chapers have deteribed the most common pack sing material and thei propertien. This chaptes shows how the ‘materials compare in general, one with another, in renga and barrier properties. Taso describes some new materi hat are finding packaging applcaiens bed on ti high performance. Barrier property comparison, ‘Two ofthe mose important properties for fod packaplog are lowe water vapour transmission face and lw gas petmieablity This ‘because dry food produess require protection fom moisture and most fod quire protection fom ondaion {Is eaty to find e pase ro provide a good water vapour bares, ‘bur the lck of «good thermoplastic oxygen barrier exible pickagin’s mos crea performance lit, ‘Some plastic lke polyolefins, ate good water vapour bers bot leak oxygen lke aries. Other, like nylon MXD-6 and [BVH are good oxygen baits but ae moisture sense PVC excels at both oxygen and moisture resistance. PET and PVC rank isthe mie range on bth properties ‘Atte isk ersimplifcaton Tables 12 nd 12.2 show the bat, ‘er propetes ofthe commodity packaging plastic. They ae ited ‘inorder increasing peemesbiy (he bet bares ae ted rs), ‘astrting the lack ocozlason between wate and caygen Dries ns136 Pckaging Materia shouldbe note thar permeability alo varies with rmperstis and humid conditions: “Tb 12.4 Wher apne uminon fee poh ane rn Soe a : - ten s fe Se eatyentre ig eC me econo is Reuse Fa Beene eer ie Reuse! # aes 4 mre ete Rea Rae “Tisnaogy (1997) p74 “ Ea SaaS Saas a Sasa Prcate oa eines ae SE an Bae = # Se ese h son # Repent 8 goa & oan & Soe 22 Bei tore 28 Sane 32 {Edt i es i Seuce Beams erie pomer? ie Wig Eaoxbpede of Pca hia 9 8 * ani beri propoies and prormancs a ‘As mentioned in Chapters 5-1, there are variation ofeach pla fis ike orientation or metallocene catalyst technologies that Improve the basic polymers barrier and suengts properties. It has algo been shown that combination materials like coext ‘Sons, lainstions and blends can optimize the proper ofeach Tuva, Chapter 13 explores thee lesa wall coatings and ther surface modifications auch er metalzation and sifcon ‘ride deposition which ea niprove spastic’ bari properties. Other high barrier plastics — HINPs and Aluoropolymers “Two other high barrier materials have been introduced to pack aging High title polymers are superior oxygen barress and ‘uoropolmers are superior wacer vapour bases. “High nite plymnecs (HINPS) ae coplymers of ail and ober plastics, Nite lone is an outstanding gat and aroma barter tn har good chemical resistance, surpassed only by PVC and EEVOH. Nites ere uid in dhe fist plastic bottles for carbonat- fd beverage becuse of tele barier prope, IND, however, have an affinity for water and are not a good trate basrer, Furthermore, rites slone is efcult co melt process because tends to degrade a temperaares below those Feguired for processing, and #0 ‘# ls copolymerized. with Comonomers which Inereae ite melt-processabiiy without reducing ts properties ® THIN can be copolymerized with many diferent polymers (ABS tnd SAN, deseribed caller ae styrenelHINP copolymers), but ‘ort ofthe packaging appicaons have involved polyleSn "They gain gor base and chemical resisance fom the HINP nd ‘wate vapous barrier and economical processing from the poly iin. When coplomeriaed with PP, HNP ema be used in high température eniromment ikea lrowe, INP ae sie dan DET PVC and he poholefins.138 Packaging Materia Rubbersmodified serylonirt-methyl acrylate (ANIMA) copoly mer (Sono Chemical tradename Bares) ts the fat HNP tn ‘commercial production whic has been approved in the USA for ‘use with foods, There have been concerts with other HPs ‘regarding the migration ofthe AN into food produc. Bares is used 10 make chemicat-resitant bottles; HNP fs the inner contac yer, mow often coeruded with HDPE. Tei se in blow moulding nd suetch blow moulding processes. Injection blow moulding is used manly for producing small bots for product lke pists correction fui and solvent. Larger bot Hes for chemical are extrsion blow moulded. Sereteh low soulding improve impact strength ‘Buret-based film is coextruded or laminated to polyolefins and sluminium foi for food packaging applications. In semi-rigid Sect form, such cocatrasions are thermoformed to make mes! tnd chesee packaging ince canbe serlized ty ether etilene ‘oxide or guna irradiation, is increasingly sed for medical product packaging huotopolymets area ls of paralfinis polymers that have sme forall of the hydrogen replaced by Sucre. Although there Ste several fzoropalymers avaiable, thee ie only one uted for peckaing, « modified polychlorourifuoroctiyiene (PCTFE) ‘Ruorpoymes, wadename Aclar or Keb. Acar isthe best water vapour barrier polymer evaiable, Tis ‘eaneparent, a good barre gates (surpassed only by EVOED, fe inert so most chemicals, rset sbresion and weathering, nd vetain ts properties over a wide tmparture Fang fom txyogenito 150°C. Acta flim con be heat scale rine hermoformes, metalized nd stlined. eis genealy laminated to another mater. The ttetest ute i laminin wita PVC for pharmaceutics liter Packs, where a high barter to moisture is required to maintain fency It is ls ted for packaging molstore-ensive mliay, tlectonic and aerospace tems where its high price can be fused. Plastic" brie proparies and perorsance 19 Mechanical strength comparison Polymer stength increases with neressing molecular mast nd ‘with ineeasing intermolecular forces but ie decreases in the presence of plasticizers. This why, a the same molecular ne, nylon and polyester ar stronger then polyolefins and patie PVCs weaker than rig PVC. ‘Table 12.3 compares the strength of the commodity packaging plastics on the basis of tenie strength and percencage elon ton at break, impact suength and tear srength, They ae listed rong inode of desrering eng (ie soget ete ‘Tense strength indicates the stese that material can resis, before breaking when suetched. For the stme amount of mates I, PET has the greatest tense strength by foal the com ‘modiy plastic, and LDPE has the lowes. Polyeabonare (described in he nex section), nitrile and ovlented polypropy. Tene alo have high tes suength “The lower density poyethenes and nylon ae the most stretchy material indicated bythe measure of percentage clongition st ‘break. This is one reason why they are used for stretch fm, HIND, HDPE, OPP and PVC are te lest seth, most rile plas, Impact stengeh is the materials resistance o breskage under & high-velocity impact. Polyearbonate, PET end PVC have the highesc impact srenge, whic Is one reson why they are used for soft drinks bouts. ‘The polyolefins have lower Impact strength ‘Tear strength combines tensile, shear and elastic propertcs to indleate the force necessey to propagate a tea. The polyetyl ‘ene have the highest tear sength. OPP, which “sppery when toxn, ha a ery low tee scat140 Packaging Macrals Ser St, W dono of hain Tb TOPR USA (985) pp 1-22 Pasi’ brie preperes and performance ua Other high performance plastics “There is family of high pecformance enginecing polrmers, ome of which have minor sen packaging, The mon notable ‘ery strong polyeabonste. This secon briefy describes i and ‘me new ingh-emperstare materia polyuredines end guid ‘ryt polymers. Polycarbonate (PO) Polycarbonate, as sun inthe tzength comparisons in the proce ing eeton, ian extremely strong polymer, Is best known for its oe sta vandal-proof glazing, police ot shields, crash helmets hd weriaabl inf feding bowen. Cie clear ough and heat reson. isthe most impact resis {anc ofall partic. Iris also expensive It bas good resistance to traer oll and slsbola, bot relatively poor resistance to alla “The praciel manufacsrer, General Bleccie Pstis has fora thumber of seare promoted it product Leran for packaging {Maeolon is competitor produced by Byer, “aly applications were for returnable milk botes inthe USA firing the late 19608 Upto 100 tips were claimed) and at this, level the fll high ene could be jst, but the bos were hot adopted inthe USA, Some school systems inthe USA have frperimented With single-serving (0.25 lige) bots ie thei, fanch programmes, Til in other countries, notably inthe UK Inve 1070s and 1980s did ot lead to seceradoption unt he 1990e when sewed interest nthe perceived benefits of mal> ‘tip sytem for milk led to some adoption in Germany, Astra, Switzerland, Kaly and the UK. Cis sed for lye sefilabe water bores (gallon capacity) "These bottles take advantage of PC's igh weight impact rei {ances encellnt opal proper, inertness snd the eility 0 Be ‘washed on the existing equipment at 70°C many ces, When, ‘oextraded with amorphous nylon, tural PC bottles can be ‘ied for enbonated denis.1 Packaging Maris PC can be srs by commercial seriiaton techniques such ‘gutoclve, ethylene oxide, gamma radiation or electron beam, taking» god marl for many medical applications. Sine it {xn wistand high hes, ti also suitable freeze and hot, food applications. beke-in pooch for partally baked bread rls Ipene fe bese Known fod packaging wes for polycrbonse PC film for packaging is coexruded with pololefin heae-seal layer. Such fm are tough and stong, and have been used to package disposable medial produc, Thicker sheets, coexruded Sieh erptallized polyester, are termofoumed into strong dusl- ‘vnable trays and blisterlelamshelle for medical products, ‘Bowes, coestruded with EVOH and PET, are used in Denmark for tomate betes they can withstand hovlling a empers= tures which PET slone could nor withstand without distortion or ‘whitening. PC ean alo be foamed to form's strong insulating aerial. High tomporacure plastics “There are some other relatively new pasts that canbe wed in hightemperature appistions. Polythermide i vigid material characterized by is high tem= peratre stably: up f0 180°C in continuous use, bat some spe ‘lie forme can go up o extremely high tempersturss, a igh 3 350°C. General Electric Parice manufactures it under the ‘ame Ultem and has produced, besides electrical componens, Coextruded sheet materiale be thermofarmed for microwate sed ovenable ce. Polyphenylene sulphide and polyphenylene oxide (PPS and PO) act two other igh temperate polymers ued manly for Consumer durable items and engineering componens. Some ‘merginal applierions have been found in packaging 00, when ‘her chemkal resistance, heat essence end'mechancal strength juny their higher costs At mentioned easier, PPO has been ‘combined with PS for microwaveble rays lat barr propre and prormance a ‘Metiylpentene copolymer (TPX) wa developed by ICH in the 1970s asa high temperature coating fr paperboard-based oven able rays. Itas temperature stability up «0 100°C. The materia as not Widely adopsed owing both t he dif in developing kable coating terhnolopis and toe advent of PET ofeing {he potential to provide a similar high temperature coating ‘much lower cost. Mitsubishi as peogeesed the pactaging applic ‘ations, producing high temperature in and moulded contin- fs for coumetice and toiletries The later aplication exploits “purl ih cary ind ae. The ata de. at 0.83 gem, i lower even than polyproplene'y, provid high ped to marginally oe ts igh ost. [Nosyeesia, developed by GE Plato is hee estat and eia- tains dimensional aby upto 197°C eis wed fr mroweeable ‘une inthe USA and Barone Poburethance Polyurethanes (PUs) ate group of thermosets that are weed ‘most in packzzing inthe form of exlslar dunnage vod filer and cushioning materials, although there are some PU fs. Fuyuehnes re cea he cea btn nt os combining an isocyanate wit «polyol (polyester, polyether or tafe polymer). “There ae two types of PU foam wed in packaging The earliest were the preformed spongy resent sheets used o protect smal, lightweight ems, This isthe same kind of low dena), pen cl, flexible PU fom ured in seat curhions and carpe padding ‘The second ype, foum-inplace spss, combine the isocyanate 1nd polyol a the paint of se. Tae te chemicals ae mise and ‘apensed ino the box, mould or & bag, where they sucky (630 seconds) react to crete for and expand to il he space, ‘Aste blowing agent expands inthe forming polyne, the el= Ine sruerure erated ad the foam rss and then sets into the soled forms77 Puchaging Matra In most applications, she product tei placed onto the expand ing foam (which i erally covered wit «polyethylene Sm) $0 thatthe foam can mould fe around the proc, uly ling the ‘od, Foameincplace material i avnnble in varios Gents nd fan be wed for various weight of product. The material expen sive compared ‘with other cushioning and void filers, but i Advantage i thatthe mould cows aze low or non-eirent. Tit ‘ft sed for aplistions where product shapes vay. Grades of polyurethanes are algo used in the form af coming nd for cera special wes ke suspension packaging, the metal ‘produced as very tous thin fm. A particular characters of {he lm ists ot el making especialy ultable fr medal snd hygiene products Isl mechanical rrength end grease restance Inne been utlized in cortsin demanding indsstal and nlitary achaging applications Graft copolymers, ionomers Graft copolymers are ¢sroup of specaiy place with useful properties in thee semismolren form. These ate desiatives of tome of the most common polymers, modified to have grafted ‘ono demain moleale certain other groups (or aia. Graft copolymers, by tei affinity to bond wo otherwiteincom= patible material, provide highly aggresive adhesives, [EVA (lscussed in Chapter 7) was an ery forms and DuPont’ Soriyn canbe used a flim or ata coating anon termediate layer in a coextuson, This sa family of materials known a8 fonomers, characterized by the presence of metalic fons i the ‘molecule. They relate closely to LDPE and the two meet ipot= ‘aor grades ere based oa ane and vdiom ons in the lyme ‘The outstanding property Benefits of these over LDPE are sreater toughness, ol and grease resistance, hot tak (physiol fKrength ducing the molten phase) and a tenacious silty 0 sedete co other surfaces, expecially metal. Thi tie of properties Pati bari proparie and peormance Ms aes ham petcuarlyaukable a a uiface comtng on paper ot ‘mult- material laminates. The toughness of the material best, ‘demonstrated bythe use of Sry fra for skin packaging which fan cover etn sharply pointed ems widhou being puncture. {Ac aheacstalable lye, fonomers provide high strength which builds up very rspily. This high suengih is achievable even if the surface is contaminated, a particular benefit for packaging ‘ly fod prodvets sucha cheee and har, A common sructare for chis application ia laminated PETinylon with an ionomer Ieatseal ayer. ‘Ocher graft copolymers incude ethylene butylaerylate EBA), ‘etilene methacrylate (EMA), ethylene acrylic acid (EAA) and ‘Shylene methacrylic red (EMAA).Allcan be produced in im form bur are moxt cost effectively ured as Blends with LDPE, ‘ inermodiote layers in cocssrusions oF as high quality heat fealable ayers Liquid cretal polymers (LOPs) ‘One fil group of materials which are all In the realm of ‘eeatt bat which could revobtionize plete eHigud erst Dolpmere (LCP). First used for ultra high performance bes (Kevlar is one), their potential wider application in film and -motlded iter has been the subject of research since the eatly 1980. “There are two misin ype of LCP. The otropic type canbe pro- doce oni directly fom solution, be spun int res o into fim vias ait die. The other group called thermotopic, holds {greater poten interest for proaging, These materiale ae char cteria bya recy harp (be narow range) melting pola. 1 thei ighly figs form, use molecules align themselves ro some ‘extent in the direction of flow, 50 providing directional igi Some people have ealed them self-eiaforcing plies for this eason, This algo contributes tothe excllens permeability es- tance vo gates, By controlling the processing conditions, the| 6 Packaging Matias ~ ley since nylon sid EVOH do not eal adbere to pelgleis, © Ti layer eed Soc ruler fm ha inelade the, Most aches laminations are made wsing a dry bond proces. A Tigi edbesive applied to one eubrtrate and fs died with hot fit This dred stiace i then adhered to cond subst using heat und pressure Tn the wet bond proces, the adhesive sapped ro one substrate tnd then the sabtrates are oined and dice together in an ove, [a eset one of he edbezeter mont be porous enouph fallow the ‘water or organi solvent to evaporate ‘Athi adhesive lamination process involves the sppication of a hhtemelt adhesive (miarue of polymers and wae) tothe sub~ ‘eats, jining thet aa cools In the related thermal process, the hett-aealble layer is applied to one substrate and then the liye see atintod when che two layers ae joined. ‘The adhesives (genealy wredanes or acrylis) are chosen 10 ‘withstand the intended processing and distribution ofthe prod- {et This may include hightemperature retortingy product with Slate organic migstion whieh may disole adhesives or other packaging components which may react and change colour. ‘Because de adhesives are reactive chomials ha are expected 9 polymerize andecromink when costed, government food adie ‘he regulators conto the presence of eny unreacted residuals ‘Barusion lamination voles exuding atl e ayer of pai {pleally LDPE) to bond together layers of fm, paper ofl “Th the method se! for making apt aie package materi- tls wich may have a8 many a seven layers including paper and foi intncaved end coated with poyetylne “The advantages over adhesive amination are lower com, eonte re nibeaive i netded and there are envionmentJ Pochging Matra mieions Th plyrylee eye provides adhesion well adding a barrier in its own right. It permits the process of thine nes ffi. At preset xtraion aminton acco ‘oethe majority of priate soul yer Bebe pecaging, ocrrson the lee pret eliminates ne thee of scary manutaced abst end reacts oS Opernion ts snl step. Sova lye of nokespeas oe Sulaneouly eared st tage wall ger sae tchumade of « spel coercion proceso bows Pure 134. or expla sige scp cotton of HE end EVA tect tiation OPP sed LDP we ol ae frei xc nd vetaon LODE coo nd Pit 9.1 Centon tn coetratos cach tc maintains identity a epazae lnyr aod can contibteraroar foneon according or ‘ample corte mwas to peciage meas yee len, ENOM and lonomer, which prone tapes, het ‘tance ome arc sd lorsnentee ag losis ad coher compos materials 17 ‘Foc some comablassions of materials, thet is insufficient sdhe= flon bereeen the two polymers, and te layer is wed. These ie layers are thermoplac adhesives which are also coexruded a & ddiganct layer Tie many coertruded matecas have chee Hyer: ‘ne of ch ofthe to desired components and one te layer ‘Structures wit our to five layers are comma, especially when EVOI i used for a barrier layer. Since EVOH is moisture fenritives it must be sandwiched between other polymers (OF ‘moisture protection, and the combinations often require te lagers oe untested previously in Table 7.2. Some combinations dat perform very well as coextusions would not function ef blends. For example, x coextrusion of EVA and fylon would behest sealable and provide an aroma baci, but if faised in blend, the two mera would ‘contaminate’ each ‘thes she alon would loe ir bare power and the EVA would ‘Serade atthe temperature necestry 10 mel the nylon. Bottles and ater rg packages can also be made by coexroson proceses, Coerruson blow moulding is decribed in Chapter 5. “There are three per of coeutruded structure. Single resin ouxtrsions have to or more lagers ofthe same resin, but each Itper is modified for special purpose. One layer may be Pi tented or reyGled resin endwiched between ign materia Couto! surface quality and mcinabilty, o one Iyer may have 1 dierent coefeiet of flor ‘Unbalanced coexrsions, often used for form=fll-seal apples tions, typicelly combine a fonctona lyer lke HDPE with ¢ hhene salable ein ike BVA. For horizontal over-wrapping, a PP farface layer is sometimes desired for is higher thermal rex ance. Anoterappiction combine cast PP which has aHimied Iencaealing range, with more sealable polyethylene for single ‘Sees of chesse.Sietch wrap can be made to be sticky on one Side and not the other by cosxtuding LLDPE with Tes taky material