Recycling
of
Plastic Materials
Francesco Paolo La Mantia
Editor
3
CP
ChemTec
Publishing
Copyright
©
1993 by ChemTec Publishing
ISBN 1-895198-03-8
All rights reserved. No part of this publication may be reproduced, stored or transmitted in any form or by any
means without written permission of copyright owner. No responsibility is assumed by the Author and the Publisher
for any
injury

or/and
damage to
persons
or
properties

as
a matter of
products
liability, negligence,
use,
or operation
of any methods,

product

ideas,
or instructions published or
suggested
in
this
book.
Printed in Canada
ChemTec Publishing
38
Earswick Drive
Toronto-Scarborough
Ontario
M1E
1
C6
Canada
Canadian Cataloguing in Publication Data
Main entry under title:
Recycling of plastic materials
Includes bibliographical references and index
ISBN 1-895198-03-8
1. Plastics
-
Recycling. I. La Mantia, F. P.
(Francesco Paolo)
TP1122.R43
1993
668.4

C93-093134-3
Table of Contents
Poly(ethylene terephthalate) Film Recycling 1
Introduction 1
Direct Re-use 3
Re-use After Modification 6
Monomer Recovery 8
Methanolysis of PET-waste 8
Hydrolysis of PET-waste 8
Incineration 10
Bio- and Photo-degradation 11
Photodegradation 11
Biodegradation 12
Conclusive Remarks 13
References 14
The Importance and Practicability of Co-injected, Recycled
Poly(ethylene terephthalate)/Virgin Poly(ethylene
terephthalate) Containers 17
Introduction 17
Basic Technology 18
Manufacturing Process of Multilayer Bottles Containing Regrind 18
Drying of PET Resin and PET Flakes 18
Co-injection Molding of Virgin and Reground PET Flakes 21
Conditioning and Stretch-blow-molding 21
Double-layer Preforms 22
Trials of Co-injecting Virgin PET and Reground PET Flakes 22
Quality of the Raw Materials 22
The Trial Processing 24
Trial Results 24
Cost Savings 24

Contamination Aspects 24
Bacteriological Contamination 24
Contamination by Foreign Substances 25
Conclusions 26
i
Recycling of Post-consumer Greenhouse Polyethylene
Films: Blends with Polyamide 6 27
Introduction 27
State of Art 28
Experimental 31
Materials 31
Structural Studies 32
Mechanical Properties 32
Results and Discussion 32
Blends 32
Coextruded films 37
Conclusions 37
Acknowledgment 37
References 37
Recycling of Plastics from Urban Solid Wastes: Comparison
Between Blends from Virgin and Recovered from Wastes
Polymers 39
Introduction 39
Experimental 41
Materials 41
Blend Preparation 42
Rheological Measurements 42
Density 42
Mechanical Properties 42
Morphology 42

Thermal Analysis
43
Results and Discussion 43
Rheology 43
Density 45
Morphology 45
Crystallization Behavior 48
Mechanical Properties 50
Tensile Behavior 50
Flexural Modulus 53
ii
Impact Resistance 53
HDPE/Heavy Fraction Blend 54
Conclusions 55
Acknowledgements 56
References 56
Management of Plastic Wastes: Technical
and Economic Approach 59
Introduction 59
Recycling of Urban Plastic Wastes 60
Experimental 62
Materials 62
Procedures and Utilities 62
Results and Discussion 64
Identification of Polymers Present in the Film Plastic Wastes
and the Rheological Behavior of the HDPE/LDPE System 64
Mechanical Behavior of HDPE/LDPE Blends 65
Microstructural Aspects of HDPE/LDPE Blends 70
The Economical Approach 80
Conclusions 81

References 81
Blends of Polyethylenes and Plastics Waste. Processing
and Characterization 83
Introduction 83
Experimental 84
Results and Discussion 85
Processing 85
Mechanical Properties 87
Blends Containing Calcium Carbonate 94
Blends Containing LDPE 97
Conclusions 98
Acknowledgment 98
References 98
Techniques for Selection and Recycle of Post-Consumer
Bottles 99
Introduction 99
iii
General Considerations 100
Molecular Separation 103
Microseparation 103
Macroseparation 104
Recycle Installations 107
Grinding 107
Air Flotation 108
Washing Equipment 108
References 108
Hydrolytic Treatment of Plastics Waste Containing Paper 111
Introduction 111
Experimental 112
Hydrolysis 113

Processing 115
Results 116
Conclusions 121
Acknowledgement 121
References 121
Processing of Mixed Plastic Waste 123
Introduction 123
Mixed Plastics from Household Waste 123
Plastics from Industrial Sectors 129
Concepts for Car Interiors 131
TPO Based Materials 132
Synthetic Leather 132
Foam Sheets 132
Technologies 134
Automotive Applications 135
Dashboard 135
Floor Covering 135
Other Components 136
Conclusions 137
References 137
iv
The Use of Recyclable Plastics in Motor Vehicles 139
Recoverable Materials in the Motor Vehicle 139
Present Recovery Practice 139
Changes in the Materials Used in Vehicles 140
The Effects of Materials Substitution on Vehicle Recycling 141
Disposal of Residuals 144
Recyclable Plastics Components 146
Preliminary Results 146
Comparison of Virgin and Recycled HDPE 146

Comparison of Fluorinated and Unfluorinated HDPE 147
Torsion Test 147
Tensile Test 147
Charpy Impact Test 147
Ballistic Test 148
Degree of Crystallinity 148
Melting Temperature 148
Flow Index 148
The Recycling of Material from Used Fuel Tanks 148
Torsion Test 149
Tensile Test 149
Charpy Impact Test 149
Ballistic Testing 149
Degree of Crystallinity 150
Melting Temperature 150
Summary and Conclusions 150
References 150
Ground Rubber Tire-Polymer Composites 153
Introduction 153
Ground Rubber Tire Composite Behavior 154
Tire Grinding 154
Characteristics of Tire Particles 155
Polymer Matrix 156
Particle Size 158
Adhesion 160
v
Matrix Modification 165
Ground Rubber Tire and Recycled Plastics 167
Conclusions 168
References 169

Quality Assurance in Plastics Recycling
by the Example of Polypropylene 171
Resource Recycling 171
Used Battery Recycling 173
Crushing and Separation 174
Further Processing to Polypropylene Granulate 175
Quality Assurance To EN 29,000 PP 176
QA Element - Raw Materials 176
QA Element - Process Control 179
Quality Assurance in After-sales Service 182
Outlook 184
References 185
Index 187
vi
Preface
Recycling of plastic materials is now an important field in the plastics indus-
try, not just an activity born under environmental pressure. The recycling pro-
cesses include industrial operations in which secondary materials are
reprocessed and/or monomers recovered for further polymerization; such pro-
cesses are termed secondary and tertiary recycling.
Although the plastics industry considered recycling for many years, attention
was mainly focused on the recycling of industrial scraps and homogeneous
post-consumer plastics which are easy to collect and reprocess. More recently,
the plastics industry accepted the challenge of recycling of heterogeneous plas-
tic waste based on new technologies of separation and reprocessing.
Scientific research, scarcely visible only a few years ago, is now a very active,
fast-growing discipline, contributing numerous papers which appear in the sci-
entific literature. Several congresses and scientific symposia are attended by
specialists every year and new books on this subject demonstrate the great sci-
entific and industrial interest in the recycling of plastic materials.

This book is intended to focus on the state of the art in recycling, the most re-
cent technologies of recycling, and some recent scientific research in the field.
Polyolefines and poly(ethylene terephthalate) (PET) are the most frequently
recycled polymers, and as such they are given significant attention in the re-
search and technology which this book reflects. Two reviews characterize the
state of the art in PET recycling. De Winter presents a review on recycling of
PET film and Neumann on a co-injection technology which allows one to use re-
cycled PETas anintermediate layerin bottles.Both processesare commonin in-
dustrial practice and are thus able to offer an overview of experience in plastic
recycling which is of interest in other areas of recycling as well. Other references
to PET recycling are presented by Sereni and La Mantia, Perrone, and Bellio.
Polyethylene (PE) and other polyolefines are discussed from various angles. La
Mantia and Curto propose methods of recycling of photooxidized polyethylene in
blend with Nylon 6. It is shown that the recycled PE behaves like a
functionalized PE, having compatibilizing attributes due to which blends ex-
hibit improved mechanical properties.
Recycling of urban wastes is discussed by Gattiglia et al. and by Laguna et al.
Generation source, separation possibilities, and cleaning technology are dis-
cussed in relation to blend properties, such as rheology, morphology, and me-
chanical properties. Comparison is also made with blends having similar
7
composition but made from virgin polymers.
The major problems in recycling of mixed plastic waste are due to their inferior
processability, which results in materials having poor mechanical properties.
La Mantia et al. and Vezzoli et al. present experimental results which disclose
the possibility of obtaining recycled materials with acceptable properties from
mixed plastic waste.
Plastic wastes are often contaminated with paper. Klason et al. present an in-
dustrial method of reprocessing paper-contaminated plastic waste which does
not require a difficult and costly separation process. Instead, cellulose from pa-

per is converted to a filler. The method and equipment suggested allow for excel-
lent dispersion of in situ formed filler.
Recycling of plastic component from car scrap is a very important challenge for
the plastics industry and car manufacturers, since the plastic content in cars is
systematically increasing. Henstock and Seidl show results on the recycling of
plastic fuel tanks, Oliphant et al. describe the methods of application of ground
discarded tires as a filler in polymer composites; Vezzoli et al. present new strat-
egies of design of easily recyclable car interiors; while Heil and Pfaff show how
battery recycling can utilize all initial components, offering quality assurance
for recycled polypropylene.
An alternative method of recycling of mixed plastic waste is based on a separa-
tion of different components into homogeneous fractions. Sereni describes op-
portunities in this area and interesting industrial equipment required for
effective separation of PET and PVC.
The above short summary shows that this book combines lessons from the past
experiences of an industrial practice with evaluation of modern trends and cur-
rent research in the field of plastic recycling.
F. P. La Mantia
Palermo, September, 1992
8
Poly(ethylene terephthalate) Film Recycling
W. De Winter
Agfa-Gevaert N.V., Research & Development, Septestraat,
B-2640 Mortsel, Belgium
INTRODUCTION
The impact of man-made polymers on the environment isa problem of high pri-
ority in most industrialised countries. Mainly due to a build-up of disposed
waste in landfills, and due to campaigns in the press about mistakes made in the
management of waste treatment, public opinion is focusing on this problem. The
fact that the corresponding percentage by volume is higher, due to the low pack-

ing density of wastes, makes the problem more visible. Although “plastics” con-
stitute not even 10 wt% of the total amount of wastes, both residential and
industrial, found in landfills (see Figure 1), public attention to them is increas-
ing. A possible explanation
1
of such a reaction suggests that there is a lack of
compatibility ofplastics withthe environment,despite the fact that the majority
of products used in present daily life are made of materials which have also been
manufactured by a chemical process.
The plastic waste in landfills consists of about two-thirds polyolefines, and
only ca. 15 % of styrene polymers, ca.10 % of polyvinyl chloride, and less than
10
% of all other polymers, including poly(ethylene terephthalate) (PET).
The largest use of PET is in the fiber sector. PET film and PET bottles repre-
sents only about 10 % each of the totalPET volumeproduced annually.
2
It is also
generally known that the total ECO-balance, considering energy consumption,
atmospheric and water pollution, as well as solid waste content, is by a factor 2
to 5 more favorable for PET film than for its greatest competitors in the packag-
ing sector, namely glass and aluminium.
3
In addition, PET is one of the largest recycled polymers by volume,
4
because it
is suitable for practically all recycling methods.
1
PET recycling by the following
technological processes is discussed below:
W. De Winter 1

• direct re-use
• re-use after modification
• monomer recovery
• incineration
• and re-use in a modified way.
In addition, attention will be given to some other attempts for recycling which
have not been thoroughly evaluated so far, like biodegradability and
photodegradation.
This paper is limited to the discussion of PET-film recycling. A global review of
PET-recycling in the sectors of fibres, films, and bottleswas publishedearlier.
2
2 PET Film Recycling
Figure 1. Composition of landfill-waste (domestic and industrial).
DIRECT RE-USE
Over 50 % of the PET film produced in the world is used as a photographic
filmbase. The manufacturers of these materials, mainly Agfa-Gevaert, East-
man Kodak, du Pont de Nemours, Fuji, Minnesota Mining & Manufacturing,
and Konishiroku have long been interested in PET film recovery. An important
motivation for the efforts made by these companies is the fact that photographic
films are usually coated with one or more layers containing some amount of
rather expensive silver derivatives, which have been recovered since the early
20th century, when cellulosics were used as a film base. Silver recovery makes
PET-base recovery more economical.
5,6
In a typical way of operation, PET film
recycling is coupled with the simultaneous recovery of silver, as represented in
Figure 2.
W. De Winter 3
Figure 2. Combined recovery of silver and PET.
In the first step of the process, photographic emulsion layers containing silver

are washed with, for example, NaOH, and after separation, silver is recovered
on one side, and cleaned PET-waste on the other side.
2
Important in this process
is that the washed PET-film scrap is clean enough to be recovered by direct
re-extrusion, although careful analysis remains necessary.
Direct recycling of PET-waste in the molten state, before re-extrusion to
PET-film, is of course the most economical process thinkable, as recovered
PET-scrap can be substituted for virgin PET-granulate without requiring any
additional steps. It is well-known that PET in the molten state gives rise simul-
taneously to polymer build-up and to polymer degradation, so that reaction con-
ditions for this process have to be controlled very carefully in order to obtain an
end-product with desired physical, chemical and mechanical properties, like
color, molecular weight, and molecular weight distribution.
A large number of reaction parameters have to be kept under permanent con-
trol (temperature, environmental atmosphere, holding time in a melt state,
amount of impurities, type of used catalysts and stabilizers, etc.). The order of
addition of the PET flakes is very important. A typical flowsheet of a
batch-PET-process
7
is represented in Figure 3. In such a process, the PET-flakes
can be added after polymerization, before the melt enters the film extruder
screw (Figure 3, indication 1). Such a procedure, however, has two main draw-
backs:
• a highly viscous melt is difficult to filter (to eliminate possible gels or
microgels)
• resulting low-boiling or volatile side-products cannot be discarded any-
more.
In order to eliminate these disadvantages, several alternative operation
modes have been worked out in the past. A method to add recycled PET during

4 PET Film Recycling
the esterification step (Figure 3, indication 2) has been described by du Pont.
8
In
such a way filtration can take place in the low-viscosity phase, and volatiles can
still be eliminated during the prepolymerisation phase.
Although PET-recycling by direct re-use is by far the most economical process,
it is only useful in practice for well characterized PET-wastes, having exactly
known chemical composition (catalysts, stabilizers, impurities). Therefore, this
process is the most suited for the recovery of in-production wastes, but it may
not be ideal for customer-recollected PET-film. An industrial process for X-ray
film-recycling was worked out by the IPR-company
9
and introduced to the mar-
ket under the name REPET on the basis of a triple motivation:
• availability of the waste chips on a repetitive basis
• suitable purity
• very competitive price.
W. De Winter 5
Figure 3. Batch process flow sheet.
RE-USE AFTER MODIFICATION
Similar to the method described under direct re-use, in which PET-flakes are
added during the esterification process, PET-polymer is broken down into
low-molecular, low-viscous fractions. Such method could already be viewed as a
method of re-use after modification. Because the intermediate products are not
separated at any moment of the process, the degree of purity of PET-scrap must
be high.
For PET-wastes having a higher degree of contamination, other technological
processes are applied, including further degradation by either glycolysis,
methanolysis, or hydrolysis,

10
yielding products which can be isolated. The prin-
ciples ofchemical processes on which these methods are based are schematically
represented in Figure 4.
6 PET Film Recycling
Figure 4. PET degradation by glycolysis, methanolysis, and hydrolysis.
Glycolysis can be considered as a method for direct re-use, whereas
methanolysis and hydrolysis are mainly taken into consideration for monomer
recovery, as discussed below.
The du Pont Company published
11
many details concerning the glycolytic recy-
cling of PET. Less costly ingredients than those required for hydrolysis or
methanolysis, and more versatility than direct remelt recycling are quoted as
the reasons for glycolysis choice. Goodyear has also developed the PET recycling
process based on glycolysis which is called REPETE.
12
Glycolytic recycling of PET, which can be done in a continuous or in a batch
process, is preferentially performed by addition of a PET waste to a boiling eth-
ylene glycol, which leads to the formation of low-molecular weight intermedi-
ates and eventually to crystallizable diglycol terephthalate (DGT). The rate of
the degradation reactions is primarily controlled by varying the holding time
and temperature, which depends on a choice of suitable catalysts (e.g., titanium
derivatives),
12,13
and by adjusting the PET/glycol ratio. It is also necessary to
avoid side reactions which might occur, e.g., by adding “buffers” or by keeping
down reaction time and temperature.
The low-molecular weight depolymerizates can be introduced directly into a
polymerization system,

14
preferentially after filtration. In this method, particu-
lar care has to be taken in order to avoid glycol ether formation, which may lead
to PET of inferior properties. The glycolytic degradation can also be pushed to
further completion, leading to DGT-recovery, rather than to direct re-use.
In addition to the glycolytic recovery of PET for production of a new PET-film,
granulate, or monomer (EG and DGT), alternativemethods have been described
for the preparation of so-called PETGs (i.e., glycol-modified PET), which can be
used for different purposes.
15,10
Depending on the type of glycol (or polyol) used
for depolymerization, and on the nature of dicarboxylic acid used for subsequent
polycondensation, the obtained polyester may be used as a saturated polyester
resin (e.g. for films, fibres or engineering plastics), unsaturated polyester resin,
mixed with vinyl-type monomers, or alkyd resin, where polycondensation is per-
formed in the presence of tri- or poly-functional organic acids.
Although this method for producing unsaturated resin, e.g., for use in regular
castings or in fiber-reinforced laminates, has been thoroughly studied by
PET-film manufacturers, it is believed that the method is not currently used in
production.
16
W. De Winter 7
MONOMER RECOVERY
Although monomer recovery is the oldest recycling method and can be used to
recover PET-waste having a high degree of impurity, it is regrettable that it is
not the most economical method. The earliest methods of PET synthesizing
were based preferentially on the use of dimethyl terephthalate (DMT), which
could be better purified than terephthalic acid (TPA), therefore methanolysis is
discussed before hydrolysis. The chemical principles of both processes are al-
ready given in Figure 4.

Methanolysis of PET-waste
The waste is treated with methanol (in a ratio 1/2 to 1/10), usually under pres-
sure at high temperatures (160-310
o
C) in the presence of transesterification and
(or) depolymerization catalysts.
17
Once the reaction is completed, DMT is
recrystallised from the EG-methanol mother liquor, and distilled to obtain poly-
merization-grade DMT. Also EG and methanol are purified bydistillation. East-
man Kodak has been using such a process for recycling of X-ray films for 25
years, and it is still improving the process,
18
e.g., by using superheated methanol
vapor, to allow the use of ever more impure PET-waste. Important factors which
have to be dealt with in this process are avoiding coloration and keeping down
the formation of ether-glycols.
Hydrolysis of PET-waste
19
Although aromatic polyesters are rather resistant to water under atmospheric
conditions, compared with other polymers, they can be completely hydrolyzed
by water at higher temperatures (and) under pressure. For practical purposes,
however, particularly to speed up the process, use has to be made of catalysts.
Acidic as well as alkaline catalysts have been studied and worked out in prac-
tice.
Figure 5 gives a flow chart of both processes. While both systems are com-
pletely realistic, their usefulness under practical production conditions remains
controversial. As far as acid hydrolysis is concerned, the large acid consumption
and the rigorous requirements of corrosion resistance of the equipment make
profitability questionable. In addition, the simultaneous (with TPA) regenera-

tion of ethylene glycol is difficult, ecologically undesirable (requiring the use of
organic halogenated solvents), and not economical. Concerning alkaline hydro-
lysis, the profitability is strongly determined by the necessity of expensive filtra-
8 PET Film Recycling
W. De Winter 9
Figure 5. Flow chart of acid- and base-catalyzed PET degradation.
tion and precipitation steps. To our knowledge, recycling of PET-waste by
hydrolysis is not practiced on a production scale at present. This situation even
persists in spite of the fact that the majority of newer industrial PET-synthesis
plants are based on the TPA-process rather than on the DMT-process.
20
INCINERATION
Another approach which can be used to recycle plastics, particularly when
they contain a large amount of impurities and other combustible solids (if such is
a case, it is important to keep them away from landfills), is more recently called
“quaternary recycling”, and consists of the energy recovery from the wastes by
burning.
21
Research along this line has been performed, particularly in Europe
and Japan, since the early 1960s. Strong emphasis has been laid on an optimiza-
tion of incinerators with regard to higher temperature of their operation and re-
duction of the level of air pollution.
PET has a calorific value of ca. 30.2 MJ/kg, which is about equivalent to that of
coal. It is thus ideally suited for the incineration process. The combustion of
plastics, however, requires 3 to 5 times more oxygen than for conventional incin-
eration, produces more soot, develops more excessive heat, and incineration
equipment had to be adapted in order to cope with these problems.
Several processes have been worked out to overcome these technological draw-
backs.
22-27

Examples include Leidner’s continuous rotary-kiln process, Baliko’s
process forglass-reinforced PET,Crown ZellerbachCorporation’s combinedsys-
tem for wood fibre and PET to provide steam to power equipment, and ETH-Zu-
rich’s fluidized bed system for pyrolysis, especially of photographic film, i.e., in
combination with silver recovery. The latter system raises the additional prob-
lem of the formation of toxic halogenated compounds, stemming from the pres-
ence of silver halides.
Typical operation conditions take place at temperatures around 700
o
C. At
lower temperatures, waxy side-products are formed, leading to clogging. At
higher temperatures, in turn, the amount of the desirable fraction of
mononuclear aromatics decreases. A representative sample, pyrolysed under
optimized conditions, yields, in addition to water and carbon, aromatics like
benzene and toluene, and a variety of carbon-hydrogen and carbon-oxygen
gases. Studies have been performed
1
to avoid formation of dioxines and disposal
of residual ashes containing heavy metals and other stabilizers.
10 PET Film Recycling
be resolved; however, quite a few residual hurdles will have to be taken
25
before
an economically feasible and ecologically accepted industrial technical process
will be available.
BIO- AND PHOTO-DEGRADATION
Although there certainly has never been a great incentive for making unstable
polymers, the idea of making photo- or bio-degradable polymers has long ex-
isted,
28,29

and quite a bit of effort has gone into research along these lines. For
such a process, of course, limitations with regard to the percentage of allowable
impurities do not exist.
Photodegradation
Special photodegradable polymers
30
were synthesized for the purpose of hav-
ing them destroyed after use (e.g., in a landfill). Another approach was the incor-
poration of suitable groups (e.g., carbonyl) in the polymer backbone in order to
make polymer photodegradable by sunlight or UV (see Figure 6). A problem
arises due to the fact that light exposure conditions on a landfill cannot be regu-
lated. Themain difficulty,however, seemsto bepractically insurmountable:it is
W. De Winter 11
Figure 6. Photodegradable monomers and polymers.
31
At present it seems that most problems arising during incineration of PET can
hardly possible to combine rapid degradation upon exposure to light in a landfill
after use with a good light-stability of the film during service. This contradictio
in terminis is probably the reason why this method never really caught on.
29
An-
other problem is a combination of desired properties withfavorable economics.
Biodegradation
The main difference between biodegradation and photodegradation lies in the
possibility to create in a landfill an environment completely different from that
encountered under normal storage conditions; e.g., microorganisms which can
destroy plastic films may be added to a landfill.
In spite of the fact that substantial research time was spent on studies in this
field, it is claimed
32

that surprisingly little is understood about the molecu-
lar-level interaction between polymers and microorganisms. This can be ex-
plained by a poorly defined environment (in a landfill), and by a large number of
complex parameters involved in the process: methods of evaluation based solely
on changes in physical properties are thus unsuitable for forming conclusions,
similar to the evaluations based only on biogas production. Specifically for poly-
esters, however, a number of interesting data are available. Esterases (ester-hy-
drolyzing enzymes) and also some microorganisms are known to biodegrade
polyesters at a reaction rate depending upon the polyester structure.
29,33
While
many aliphatic polyesters, specifically poly(hydroxy fatty acids) - e.g., the
BIOPOL
34-36
packaging material commercialized by ICI - are suited for
biodegradation, the aromatic polyesters (e.g., PET) do not possess this prop-
erty.
32,37-39
Another approach consists of mixing small amounts of biodegradable poly-
mers, e.g., polysaccharides, with a regular polymer (e.g., a polyolefin), in order to
make the end-product destroyable as well. Examples of polysaccharides/poly-
ethylene have been commercialized.
38
Mixtures of starch with other polymers,
40
12 PET Film Recycling
including PET, have been studied,
34
but no commercialization of the latter mix-
ture is known so far. The fact, however, that the starch additive is only needed in

small amounts, which hardly alters the properties of an original polymer, might
show some promise for future applications. One has to realize, however, that the
thermal stability of starch derivatives above 230
o
C is limited, whereas the
PET-film extrusion temperature is in the range of 280
o
C. There also remain
some controversies about the completeness of the degradation of polymer/starch
mixtures.
Although the development of biodegradable plastics is still in progress, it is be-
coming evident that the enormous market potential, forecast someyears ago, re-
quires a real breakthrough in order to be attained.
41,42
The main reason for this
setback is probably the fact that organic polymers do not biodegrade fast
enough.
43,44
CONCLUSIVE REMARKS
• From the data presented in this overview, it seems obvious that there ex-
ists a clear hierarchy in PET-film recycling technologies. The most impor-
tant criteria of classification are, first of all, the degree of “purity” of
PET-scrap to be handled, and secondly, the economics of the process.
• For the cleanest PET grade, the most economical process, i.e., direct re-use
in extrusion, is self-explanatory.
• For less clean PET samples, it is still possibleto re-use them after the modi-
fication step (partial degradation, e.g., by glycolysis) at a reasonably low
price.
• More contaminated PET-film waste must be degraded into the starting
monomers, which can be separated and re-polymerized afterwards, of

course, at a higher cost. At present, only the methanolysis process is ex-
ploited industrially, as opposed to hydrolysis processes, which are kept in
reserve.
• Finally, themost heavily contaminated PET-shreds have to be incinerated.
Here, however, economics may not be favorable enough for industrial de-
velopment. As an alternative, those PET-shreds are brought to a landfill.
Perhaps in future more attention will be given to modification of PET-films
in such a way that they may become biodegradable, if the process can be ac-
celerated or if a real breakthrough becomes available.
W. De Winter 13
REFERENCES
1 F. P. Boettcher, ACS Polymer Preprints, 32 (2), 114 (1991).
2. W. De Winter, Die Makromol. Chem., Macromolecular Symposia No. 57, 253 (1992).
3. Anon., Plastics Bulletin, 174, 6 (Jan-1992).
4. N. Basta et al., Chem. Eng., 97, 37 (Nov-1990).
5. Brit. Pat. 1.476.539 (1977) to Barber-Colman Co.
6. Anon., Manufacturing Chemist, 66, (Mar-1987).
7. L. Hellemans, R. De Saedeleer, and J. Verheijen, US Pat. 4,008,048 (1977)
to Agfa-Gevaert.
L. Jeurissen and F. De Smedt, Brit. Pat. 1,486,409 (1977) to Agfa-Gevaert.
J. Tempels, Brit. Pat. 1,432,776 (1976) to Agfa-Gevaert.
8. W. Fisher, US Pat. 2,933,476 (1960) to du Pont.
9. J. Burke, in Plastics Recycling as a Future Business Opportunity, Technomic
Publishing Co, Pennsylvania, USA, (1986).
10. K. Datye, H. Raje, and N. Sharma, Resources and Conservation, 11, 117 (1984).
11. D. Gintis, Die Makromol.Chem., Macromolecular Symposia, 57, 185 (1992).
12. R. Richard et al, ACS Polymer Preprints, 32 (2), 144 (1991).
13. A. Petrov and E. Aizenshtein, Khim. Volokna, 21 (4), 16 (1979).
14. US Pat. 3,884,850 to Fiber Ind.
15. Anon., Mod. Plast. Int., 20, 6 (1990).

16. A. M. Thayer, Chem. Eng. News, (Jan. 13, 1989).
17. Brit. Pat. 784,248 (1957) to du Pont.
18. Anon., Eur. Chem. News, 30 (Oct. 28, 1991).
19. H. Ludewig, Polyester Fibers, Chemistry and Technology, Wiley Int. Publ., 1971.
20. H. Schumann, Chemiefasern Textil, 11, 1058 (1990).
U. Thiele, Kunststoffe, 79 (11), 1192 (1989).
21. T. Randall Curlee, The Economic Feasibility of Recycling, Praeger Publishers,
New York, 1986.
22. Leidner, Polymer Plastics Techn. & Eng., 10 (2), 199 (1978).
23. S. Baliko, Energiagazdalkodos, 28 (11), 496 (1987).
24. D. Vaughan, M. Anastos, and H. Krause, Rpt. Battelle Columbus Lab.,
EPA-670/2-74-083, (Dec-1974).
25. R. Hagenbucher et al, Kunststoffe, 80 (4), 535 (1990).
26. K. Niemann and U. Braun, Plastverarbeiter, 43 (1), 92 (1992).
27. W. Kaminsky et al., Chem. Ing. Techn., 57 (9), 778 (1985).
28. Guillet, Chem. Eng. News, 48, 61 (May 11, 1970).
29. F. Rodriguez, Chem. Techn., 409, (Jul-1971).
30. G. Smets, Chem. Magazine, 481, (Sep-1989).
31. Brit. Pat. 1,128,793 (1968) to E. Kodak.
32. G. Loomis et al., ACS-Polymer Preprints, 32 (2), 127 (1991).
33. R. Klausmeier, Soc. Chem. Ind., London, Monogr., 23, 232 (1966).
34. Anon., Neue Verpackung, 1, 50 (1991).
35. J. Emsley, New Scientist, 50, 1 (Oct. 19, 1991).
14 PET Film Recycling
36. A. Steinbuchel, Nachr. Chem. Techn. Lab., 39 (10), 1112 (1991).
37. P. Klemchuk, Mod. Plastics Int., 82, (Sep-1989).
38. J. Evans and S. Sikdar, Chemtech, 38, (Jan-1990).
39. K. Joris and E. Vandamme, Technivisie, 179, 5, (1992).
40. R. Narayan, Kunststoffe, 79, 1022 (1989).
41. N. Holy, Chemtech, 26, (Jan-1991).

42. A. Calders, Technivisie, 156, 8 (Nov-1990).
43. Anon., Mod. Plast., 20 (1), 72 (1990).
44. H. Pearce, Scient. European, 14, (Dec-1990).
W. De Winter 15