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 [...]... density of wastes, makes the problem more visible Although “plastics” constitute 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 increas1 ing A possible explanation of such a reaction suggests that there is a lack of compatibility of plastics with the environment, despite the fact that the majority of products... 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 repre2 sents only about 10 %... This paper is limited to the discussion of PET-film recycling A global review of 2 PET -recycling in the sectors of fibres, films, and bottles was published earlier Figure 1 Composition of landfill-waste (domestic and industrial) W De Winter 3 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, Eastman... discussed below 11 The du Pont Company published many details concerning the glycolytic recycling 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 12 process based on glycolysis which is called REPETE Glycolytic recycling of PET, which... 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, 10 methanolysis, or hydrolysis, yielding products which can be isolated The principles of. .. molecular weight, and molecular weight distribution A large number of reaction parameters have to be kept under permanent control (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 7 batch-PET-process is represented in Figure 3 In such a... Winter 1 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 is a problem of high priority 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... 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 5,6 PET-base recovery more economical In a typical way of operation, PET film recycling is coupled with the simultaneous recovery of silver, as represented in Figure 2 Figure 2 Combined recovery of silver and PET 4 PET Film Recycling. .. preferentially performed by addition of a PET waste to a boiling ethylene glycol, which leads to the formation of low-molecular weight intermediates 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 12 ,13 derivatives), and by adjusting... described for the preparation of so-called PETGs (i.e., glycol-modified PET), which can be 15 ,10 used for different purposes 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 . Flotation 10 8 Washing Equipment 10 8 References 10 8 Hydrolytic Treatment of Plastics Waste Containing Paper 11 1 Introduction 11 1 Experimental 11 2 Hydrolysis 11 3 Processing 11 5 Results 11 6 Conclusions 12 1 Acknowledgement. 11 6 Conclusions 12 1 Acknowledgement 12 1 References 12 1 Processing of Mixed Plastic Waste 12 3 Introduction 12 3 Mixed Plastics from Household Waste 12 3 Plastics from Industrial Sectors 12 9 Concepts. of Materials Substitution on Vehicle Recycling 14 1 Disposal of Residuals 14 4 Recyclable Plastics Components 14 6 Preliminary Results 14 6 Comparison of Virgin and Recycled HDPE 14 6 Comparison of