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ALDO JAVIER GUZMAN DUXTAN
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34 views15 pages

Us 8202379 B1

Uploaded by

ALDO JAVIER GUZMAN DUXTAN
Copyright
© © All Rights Reserved
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co» United States Patent DeLong et al. [US008202379B1 (10) Patent No.: (45) Date of Patent: US 8,202,379 BI Jun. 19, 2012 (sa) os oO en @ on, (2) (58) NATURAL FIBER WELDING Inventors: Hugh C. DeLong, Waldorf, MD (US) Paul C. Tralove. Annapolis, MD (US) Luke M. Haverhals, Annapolis, MD (US), William M. Reiehert, Annapolis, MDS) Assignoe: The United States of America as represented by the Seeretary of the Air Force, Washington, DC (US) Notive: Subject o any disclaimer, the tem ofthis patent is extended or adjusted under 35 USC 15405) by 232 days Appl. No: 121629,918 Filed: Dee. 3, 2009 Int. Dod 1100 (200601) coos 5700 (200501) us.cl 15608; 156/206; 156305 Field of Classification Search 1561296, 1560305, $3 See application file for complete search history References Cited US. PATENT DOCUMENTS, 1/2008. Mpftymaki ct 12009 Champ et e216 44423 FOREIGN PATENT DOCUMENTS Wo 2007x2022 + y2007 wo * cited by examiner Primary Examiner — Katarzyna Wyrozebski Lee Assisian Examiner —Soott W Dodds 4) Attorney, Agent, or Firm —AFMCLOAAZ: Bart Hers on ABSTRACT Natural fiber welding is process by which individual bers fre swollen by an appropriate inc igui-hased solvent sy tem fo form a congedled network, Manipulated fibrous mate Fials may be either composed of natal polymers such os cellulose, hemicellulose, silk, etcetera, or synthetic poy ‘mers, oF mixed materials. The process is principally con twolled by the composition of the solvent system which ‘includes an ionic liquid solvent pus additives such as water, riethano, et cetera, Other conditions sve as the amouat and placement of solvent, as wel os time, temperate, and pre Sure contro the extent to which neighboring fibers are fsed (aly the material atthe cuter surface of fibers need be sul cieatly mobile tomenge withthat of neighboring fibers. Mate rial inthe fiber cone may be leftin the native sate By conto Ting process variables, Fiber form acongealed network upon removal of the ionic liguid-based solvent. 10 Claims, 9 Drawing Sheets US. Patent Jun. 19,2012 Sheet 1 of 9 US 8,202,379 B1 US. Patent Jun. 19,2012 Sheet 2 of 9 US 8,202,379 B1 US. Patent Jun. 19,2012 Sheet 3 of 9 US 8,202,379 B1 or os US. Patent Jun, 19, 2012 Sheet 4 of 9 US 8,202,379 BI 1 | 4000 Intensity (Counts) 20 25 30 35 20 (Degrees) Fig. 5 D. \ 37503500 3250 3000 4500 1250 1000 750 500 Wave Number (cm) Fig. 6 US. Patent Jun. 19,2012 Sheet 5 of 9 US 8,202,379 B1 Larner US. Patent Jun. 19,2012 Sheet 6 of 9 US 8,202,379 B1 US. Patent Jun. 19,2012 Sheet 7 of 9 US 8,202,379 B1 Fig. 10 Fig. 1 US. Patent Jun. 19,2012 Sheet 8 of 9 US 8,202,379 B1 ee i ee Aaa ee) eae TE Ze )) US. Patent Jun. 19,2012 Sheet 9 of 9 US 8,202,379 B1 US 8,202,379 BI 1 NATURAL FIBER WELDING RIGHTS OF THE GOVERNMENT The invention described herein may be manufactur and used by or for the Government of the United States forall ‘governmental purposes without the payment of any royalty BACKGROUND OF THE INVENTION The invention relates tothe partial dissolution of nator fibers forthe purposes of structural and chemieal mexiiea- Synthetic polymers such as polystyrene are routinely welled using solvents suchas dichloromethane. Natural fiber ‘welding isa process by which biopolymer fibers are fused in manner roughly analogous to traditional plastic welding. Prior io the discovery that ioe igus Ge, I-ethy1--melh- ‘ylimidazolium acetate) ean dissolve biopolymers (i.e celhi- jose and silk) without derivatization, there were no analogous. 2 solvents for natural materials In ddition tothe wilizaton of an ionic liquid, control over the presence and amount of molecular additives (ie, Water, methanol, et etera)is essen- til to controlling solvent ellicae. The demonsiration of pro- ‘ess contro] by careful manipulation of molecular additives is ‘fundamental feature that set this vention apart from pre vious work. (Previous disclosures and patents exclusively invoke the utilization of neat or pure” fone Higuids and do not recognize the vital importance of molecular additive con- trol) “There are many examples in both literature and patents of biopolymer solutions tit ae east inlo molds 1 create a desired shape, In al ofthese cases, the biopolymer is com= pletely dissolved so thatthe orginal structure is fully dis- rupted. With fiber welding, the fiber interior is intentionally Teft in its native state. This is potentially advantagoous beau the final stractre retains some of te orginal mate= Fial properties and is significant for creating materials from biopolymers such as silk and cellulose Traditional methods of east molding biopolymer solutions are also disadvantaged in that there is a piysical limit to how ‘uch polymer can be dissolved in solution, Typically, soln- tions that are 10% by mas biopolymer (80% by mass ionie liquid solvent) are generally quite viscous and difficult to handle, even at elevated temperatures. The fiber welding pro- ‘ess allows (dry) fiber bundles to be manipulated into the ‘desired shape before welding commences. Te use and han ‘ding of native fibers often grants contol aver the engineering ‘of the final product that is not posible for solution based technologies SUMMARY OF THE INVENTION The invention is @ process by which individual natural fibers such as cellulose, chitin, chitosan, collagen, hemicel- lulose, lignin, silk et cetera are swollen by an appropriate ionie liquid-based solvent system, and then revonsiuted 0 form a congealed network. A cartoon of the fiber welding process is shown in FIG. 1. During welding, fiber bundles are swelled and mobilized by an appropriate inie liquid-based solvent system, for example, l-ethy13-methylimidazolium (4) acetate (~, abbreviated [EMI] [Ac], with molecular add- tives (aot shown), Nove that only the polymer atthe outer surface need be sifficently mobile to merge with that of neighboring fibers; materia in the fiber eore may be Fein its native state, The depth of solvent penetration and the degree to which fibers are welded together is controled by the nature 2 (composition) and amount of solvent, temperature, pressure, spacing ofthe fibers, t cetera Solventremoval leaves welded fibers. In ation to polymer movement, chemical deivati- ation may also be underiakea ding this process. In general, the process increases the material density and decreases the surface area ofa bundle of fibers, The mobilized fer sheath may be modified with materials such as clay, carbon nano- tubes, ron oxide, titanium dioxide, etcetera, aft elec- ‘onic, spectroscopic, thermal conductivity, magnetism, and antibacterial properties, Inadition to repiospecii alteration of the physical properties, spatial eontol of chemical prop- tees is also possible. Chemical properties (e. hydropho- reactivity) atthe fiber surface may be ether similar, ‘or significantly different from the eore (ative fiber) depend. ing on choice of derivatization. [BRIEF DESCRIPTION OF THE DRAWINGS: FIG. 1s carton of the fiber welding process. FIG. 2 shows images of cotton eylinders before and after fiber welding with an [EMI] [Ac]-based solvent system, FIG. 3 shows SEM images of intersecting cotton thread at IG. 4 shows SEM images of intersecting cotton thread at various teatment times. FIG. is aplot of powder XRD data for native and treated cotton cloth, FIG. 6is a plot of FTIR spectra data for native and treated cotton cloth FIG. 7 shows SEM images of untreated and treated silk fibers. IG. 8 shows SEM images of untreated and treated cotton fibers, FIG.9 shows images of silk belore and after fiber welding ‘with an [EMI] [Ac]-based solvent system. IG. 10 shows a spring made of hemp. FIG. 1 shows examples of “alucless sewing”. FIG. 12 shows SEM images of filler paper treated to ‘manipulate the pote size. FIG. 13 shows SEM images of cotton cloth modified with 1 surface cot of clay DETAILED DESCRIPTION [Natural fiber welding isa processing technique by which natural fibers areswollen by an appropriate onic Higuid-based solvent system for the purpose of subsequent physical or chemical manipulation. The solvent system must be capable of interrupting intermolecular bonding (atleast patil) 10 ‘pea and mobilize (solvate) the polymer far modification Molecular additives such as water, methanol, et ceter are meticulously controlled to modify the solvent eiaey. Add tionally, the amount of solvent (relative to polymer) is often intentionally Kept low to Tmitthe degree to which materials ‘are modi, Theonic iquid-based solvent may be removed tither by a second solvent system or by evaporation if the Welding solvent is sufficiuy volatile. (The evaporation rate ‘nay be increased significantly by placing the sample under vacuum.) Asused herein the term “ionic liquid” refers to aliquid that is comprised of anions and cations. lonic liquids areattractive solvents s they re non-volatile, non-flammable, havea high ‘hermal stability, are relatively inexpensive to manufacture, are environmentally friendly, and can be used to provide treater control and flexibility inthe overall processing meth- ‘odology. Ionic liquids of interest exist as Fguids well below ‘oom temperature up toa temperature a high s 200°C. US. US 8,202,379 BI patent application Ser. No, 11/326,678, filed on Dee, 29, 2005, and incorporated herein by reference, contains mumer- ‘ous examples of suitable joni figuid solvents for use inthe present invention. Preferably the sone liquid solvents have ‘melling points below 150° C.- more preferably, below about 10" As used herein the term “ionic liquid-based solvent” refers to aliquid containing anionic liquid mixed with at least one ‘other molseular component. Molecular components can be solvents such as water, methanol, etcetera that ean strongly interact withthe cations andor anions ofthe fone liquid. The method for natural fer welding comprises partially lissolving either biopolymers or synthedc polymers with a molten ionic liguid-based solvent wherein Said ionic lg solvent component is comprised of cations andanionsandhas ‘smelting point below 150° C, Theionieliquid-based solvents utilized eontain molecular species that modify solvent ‘cacy (with respect to dissolution of polymers), Whereas pre Vous work (patents) teach and detail the use of neat (pure) joie liquids, the present disclosure details the uilization of systems that are fone Tiquid(s) with a lest one molecular ‘component, The addition molecular components allow pro ‘cessing to be accomplished with much improved levels of ‘contol and are essential to the reation of advanced compos= ite materials. Additionally, ionic liquids may be diluted by a molecular solvent (generally @ non-solvent forthe partially «dissolved polymer materials such thatthe partial dissolution process of the biopolymers or synthetic polymer materials ‘Commences pon removal ofthe diluent by heating o simple ‘evaporation. The diluent may be a molecular solvent such as Water, alcohols, or kotones (or mixture ofthese). The solvent system partially dissolves biopolymer or synthetic polymer materials o fom a congealed network, Removal ofthe ini Tiquid-based solvents generally accomplished by combining ‘hemixturewith lage excess of non-solveat forth partially dissolved polymer materials that lecches the tonic liquid nto ‘a pase separate Fom the solidified materials. This washing method removes any excess ionic liquid-based solvents from the fiber surface as well as dialyzing away the solvent system from the congested fiber network. Solvents used to remove theionie liquid) from treated materials are generally similar to those previously mentioned as potential molecular diluents (Ge, water, meianol), “The Fiber welding process facilitates the eretion of func- tional sractures from the controlled fusion of brous threads, woven materials, or fbsous mats. The physical and chemical properties of said material are reproducibly manipulated by rigorous conteol ofthe amount a fone liguid-based solvent applied, the duration of exposure to ionic liquid temperature, the temperature and pressure applied during the treatment “Materials may be joined to ereate laminate stroctres with proper contol of process variables. The surface of these materials may be preferentially modified while leaving some ‘of the material in the native state. Surface modifiations ray include manipulation of Uke material surface chemistry sliretlyorindiretly by theadditionof particles to impart the ‘desired physical or chemical properties. ‘An example of the fiber welding process is detailed in FIG. 2 and includes images of cotton eylinders before (A), and after (B,C, and D) fiber welding with a solvent system con- taining I-chyl-3-methylimidvolium acetate ([EMI] [Ac] and water. Cotton thread (Wellington 3 Tb Twisted Cotton Post Tivine) was coiled around atest ube (A) and was soaked ina batho the joni liqnid-hased solvent for several minttes Cotton coils were removed from ba, excess solvent was ently brushed away, and Were placed in an oven at 6 C. for ‘one, two, and three days, respectively. Coils were then » 4 Jmmersed in double disiled water for shout 12 hours upon removal from theoven (endo treatment). Water in the cog Jatin bath was replaced several times to fully remove the ‘nie liquid. Upon remeval of the ionic liquid, the coils were placed in an oven at 80° C. While drying, the coils were ‘observed to contract and densify to create solid cylinders, Image B shows throe cylinders after processing. Cylinder BI has boon exposed to the solvent system for | day ylinder 2 or 2 days, and eylinder B3 for 3 days. Note that the contra tion ofthe eylinerength is greater for longerexposures. Dry cplinders were observe to bestrong and stiff. Pancls Cad D show Seanning Elzetron Microscopy (SEM) images of the «eross-section of several threads from one ofthe welded ey Inder (eylinder B3)- Image shows thatthe outer portion of tech thread has been fised to its neighbors. Image D shows that individual fibers that make up each thread arealso welded together and contribute to te treated coils enanood cigiity 1. Important Fiber Welding Variables Inaditiontothe choice of solvent andthe typeof material ‘eeated, three process variables principally determine the out- comcof the welding process time (of treatment) temperatire (oftreatment, and the concentration of solvent eatin of sol- vent t© treated material). The impact of each variable is described in the examples that follow, 1A Treatment Time FIG. 3 shows SEM images of the intersection of cotton threads (cellulose) welded together by exposure to an [EMI] [Acl-based solvent system, Junctions wer exposed 1950. ‘of[EMI] [Ac] after which the solvent is removed by immer sion in water Image A shows a native (untreated) cotton thread junetion, Image B shows a similar juetion after five minutes of treatment followed by a thorough ine in water remove the ionic Higuid-base solvent Images Cand D show junetions after treatments of twenty and eighty minutes, respectively, As evident inthe images, threads are progres- sively joined with inereasing exposure time to the solvent system. FIG, 4 shows SEM images fora similar experiment with hemp fibers. (Hemp differs from eotton in the composi- tion of cellulose, hemicelluloses, and Hignin.) Panel A shows the native intersection while panels B,C, and D show june- ‘ions treated with ~$0 pL of [EMI] [Ac] at 60° C. for five, twenty, and eighty minutes, respectively. As with cotton, hemp fibers fuse more completely asthe exposure time to [EMI] [Ac] increases 1B, Tresiment Temperature Imaddition to treatment time, temperature i also extremely Jmportant in determining the extent to whieh fibers are modi- fied during the welding process. X-Ray Didimction (XRD) (FIG. 8 and Table D, Fourier Transform Infrared Spectros- copy (FTIR) (FIG. 6), and tensile testing (Table TT) data comparing welded cotton cloth aid to quantify the effect of temperature and time on the welding process. The model system studied was Regency 22 eount cotton loth processed with 1.3 g [FMI] [Ac]-based solvent (with ‘addvional water and aoetie aeid 0 congo! solvent system elicaey) applied per em? of cloth for five, ten, and thirty ‘ines at room temperature and 80° C., respectively. Note that the applied rate of ionic liquid is similar to the cotton cloths density and thatthe cloth was stretched and pinned ‘over a rigid polystyrene plate during processing to prevent Significant contaction of tated samples, The ionic Tiguid- based solvent was removed by immersion in water. small pieee of cloth was also completely dissolved (in [EMI] [Ac]- based solvent) and then reconstituted in water for compar tive purposes. US 8,202,379 BI 5 Powder XRD data (FIG, 5 and Table 1) show structural ‘changes occurring with time and temperature of treatment. Plot designations in FIG. § are as follows: A~native cloth, B-welded 30 min at 20° C,, C-welded 5 min at 80° C, D=cloth that was completely dissolved and then reconst tuted. The patter for native cotton (curve A) is typical for

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