MATERIAL / RECYCLING

PET – its production,

composition, quality analysis
and processing
“Polyester bottle resins he details all of the raw materials and
answers such questions as “What is
- Production, Processing, DMT?”, “What role do co-monomers
Properties and Recycling” is play?”
the title of a recently pub- The way that PET is produced
lished book in the “PET- from the basic building blocks is fully
described, with a clear explanation of
planet Print” series. As the melt phase polycondensation (MPP)
title suggests the new book and solid state polycondensation
is a comprehensive exami- (SSP). The explanations are backed
up by equations for those who wish
nation of PET production
to understand the processes in more
and processing, focussing in depth.
particular on bottle resin.
Why so many kinds
The author of the book, Dr Ulrich
of PET resin?
Thiele, is an acknowledged inter-
national expert on the subject of We all know that mineral water
polyesters. Today he is head of the packaging does not require the same
Polyester Technology consulting serv- grade of resin as, for example, a
ice in Bruchköbel, Germany. Before carbonated beverage - but why?
establishing an independent consult- What are the fundamental differences
ing service Dr. Thiele was engaged between the various grades, and how
for more than 30 years in almost all is IV and AA content controlled and
facets of polyester production, R&D adjusted. A key aspect of PET bottle
and recycling. manufacture is crystallisation. Dr.
Specifically the new book covers: Thiele explains why a higher level of
 PET resin production crystallisation is important for hot fill
 Resin types and their composition applications, and why heat set resins
 Resin quality and its impact on the contain lower levels of co-monomer,
final product and less DEG.
 Physical and chemical analysis of
PET resin Is the resin fit for purpose?
 The handling and processing of
PET resin The characterisation and quality
 Additives - what they are and an control of PET resin and intermediate
outline of their uses or final products calls for numerous
 Polyester bottle recycling analysis methods and related labora-
 Alternative bottle and packaging tory hardware. The successful execu-
polymers. tion of such methods also requires
well-trained laboratory technicians.
So what exactly is DMT? With PET resin becoming more and
more a standard bulk material, and
This, and many other similar bottle production today being a highly
questions are asked every day by competitive mass-market activity,
PET resin users. The author presents expenditure on quality control tends to
scientific information in a mature way, be kept to a minimum. From this point
without over-simplification. For exam- of few it is important to establish what
ple, in the chapter on PET production is the “right“ amount of analytical work

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 MATERIAL / RECYCLING
in relation to the business of the resin 1990s. Nevertheless the variety of alternative at the moment. Never-
processor. Selective combination of PET materials, additives and blends theless other polymeric materials of
methods, cooperation, external exper- means that the increasing popularity similar properties in processing at a
tise and close relations with suppliers of PET enjoyed by the resin producers comparable price level and useful for
are all aspects discussed in the book. is becoming an increasing nightmare specific applications can be obtained.
Dr Thiele gives some initial guidelines for the recycling industry and calls for The last chapter of the book looks one
for the establishment of a laboratory sophisticated sorting and decontami- by one at these alternatives, includ-
for chemical and physical analysis of nation technologies. ing metallocene-based polypropylene,
PET resin, and the type of tests that Dr Thiele reviews the current and of course PLA, together with their
can be carried out. Since this is not status of post-consumer PET collec- thermal data and their potential uses.
a realistic proposition for most small tion, flake production and recycling Taken altogether this new PET-
converters an extensive listing of con- and the various technologies in use. planet Print publication is a genuinely
tract analytical labs is also given. He makes regional comparisons, pro- useful book for processors, convert-
vides estimates of future growth, and ers and bottle blowers, as well as
Storage, handling and lists equipment and system suppliers. students and trainees in the plastics
packaging industry. It is a technical
preparation for processing
Can PET be replaced? introduction to the whole spectrum of
Having accepted a shipment PET production and processing, pre-
of PET resin it is important for the An alternative to standard PET sented in a clearly-expressed manner
converter to treat the material cor- resin would be a second polymeric that not only describes the way that
rectly. PET is susceptible to degrada- material which is able to replace PET PET behaves along its journey from
tion in many ways, including friction resin in all of its applications. Accord- the manufacturing plant to the filling
and overheating during conveying, ing to this definition there is no real line, but also explains the “hows” and
which can result in fish-eyes, specks, the “whys”.
and other quality defects in the pre-
form. The author points out some of
the dangers and common mistakes
that converters make in storing and
conveying resin within the plant, and
makes specific recommendations in
this respect.
The drying of the resin is a critical PETplanet print Vol. 5:
aspect of PET processing and one Polyester Bottle Resins
which is considered in some depth, Production, Processing,
differentiating between the drying of
Properties and Recycling
amorphous pellets and the drying of
SSP pellets. The drying of amorphous Dr. Ulrich K. Thiele
pellets is carried out in two steps - Over 300 pages, with colour illustrations
crystallisation and drying. SSP pellets * prices in EUR + VAT.
are always crystalline, and so call for ISBN: 978-3-9807497-4-9 € 149.–*
a different drying process.

Additives
The wide range of applications
for PET means that the standard
material frequently has to be modi-
fied to provide optimum performance
characteristics. The additives that are
used may be CO2 and oxygen barrier,
colours, UV and IR absorption, AA
or oxygen scavengers, antistatics,
anti-friction additives etc. Dr. Thiele’s
book lists the various PET additives
which are used for specific purposes
and explains their function, as well as
pointing out any negative side effects.

Recycling
Following initial pioneering work
on PET recycling in the 1970s new
recycling processes and companies
popped up like mushrooms during the

PETplanet insider Vol. 8 No. 07+08/07 www.petpla.net 17