Degradation, Stabilization, and Recycling of Packaging Materials

Muhammad Rabnawaz, PhD is an Associate Professor for the Michigan State University (MSU) School of Packaging. Susan E. M. Selke, PhD is Professor Emeritus in the Michigan State University (MSU) School of Packaging. Ian Wyman, PhD is a Professional Aide in the Michigan State University (MSU) School of Packaging.

• Preface xiii1 Introduction 11.1 General Introduction 21.2 What Are Some Ideal Properties of Packaging? 21.3 Liquid Resistance and Barrier Properties 31.4 End-of-Life (EoL) Outcomes 41.5 Life-Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) 41.6 Open-Looped Versus Closed-Loop Processes 51.7 Recycling 61.8 Biodegradable and Compostable Packaging 71.9 Concluding Remarks 7References 82 Plastics 112.1 Introduction 112.2 How Are Polymers Named? 122.2.1 Classification of Polymers 122.2.1.1 Classification Based on the Polymer Structure 122.2.1.2 Classification Based on the Mechanism 132.2.1.3 Classification Based on the Source 132.2.1.4 Classification Based on Cost and Performance 142.2.1.5 Classification Based on Thermal Behavior 152.3 Molecular Architecture 152.3.1 Homopolymers and Copolymers 162.3.2 Polymer Molecular Weights 162.4 Polymer Characterization Techniques 192.4.1 Nuclear Magnetic Resonance Spectroscopy 202.4.2 Size Exclusion Chromatography 222.4.3 Viscosity 232.5 Microscopy Techniques 242.6 Physical State of a Polymer 242.7 Thermal Transitions 262.8 Mechanical Properties 272.9 Degradation of Polymers/Plastics 282.9.1 Overview 282.9.2 Impact of Degradation on Polymer Properties 292.10 Wanted Versus Unwanted Degradation in Polymers 292.10.1 Unwanted/Undesirable Degradation 292.10.2 Wanted/Desirable Degradation 302.11 Do all Polymers Degrade at the Same Rate? 312.11.1 How Can We Know if a Polymer Is Stable or not Against a Particular Degradation Environment? 312.12 Types of Polymer Degradation 322.12.1 Thermal Degradation 332.12.1.1 The Chemistry of Thermal Degradation 352.12.1.2 Some Polymers Degrade by Unzipping and Others by Random Scission 382.12.2 Oxidative Degradation 432.12.3 Photodegradation 512.12.4 Chemical Degradation 562.12.4.1 Hydrolysis 572.12.4.2 Environmental Stress Cracking 582.12.4.3 Other Chemical Reactions 592.12.4.4 Summary of Chemical Degradation Susceptibilities of Various Polymers 592.12.5 Mechanical Degradation 612.13 Methods for Studying Polymer Degradation 622.13.1 Weathering 632.13.2 Thermal Degradation 642.13.3 Photochemical Degradation 642.13.3.1 Change in Molecular Weight 642.14 Stabilization of Polymers 652.14.1 Antioxidants 652.14.1.1 Chain-breaking Electron Acceptors (CB-A Antioxidants) 662.14.1.2 Chain-breaking Electron Donors (CB-D Antioxidants) 682.14.2 Peroxide Decomposers 712.14.2.1 Stoichiometric Peroxide Decomposers (PD-S) 722.14.2.2 Catalytic Peroxide Decomposers (PD-C) 732.14.3 Metal Deactivators (MDs) 732.14.3.1 UV Light Absorbers and Other Light Stabilizers 742.14.3.2 UV Light Absorbers (UVA) 742.14.4 Quenchers of Photo-excited States 752.14.5 Special Stabilizers 772.14.6 Drawbacks of Stabilizers 782.15 Summary 82Problem Set 82References 833 Wood 873.1 Introduction 873.2 Wood Degradation 873.2.1 Weathering 883.2.1.1 Effects of Various Influences on Weathering 893.2.1.2 Effects of Wood Composition 893.3 Chemical Degradation 943.4 Biological Decomposition (Decay) 94Problem Set 97References 974 Paper Degradation and Stabilization 994.1 Introduction 994.2 Durability and Permanence 1004.2.1 Quality of Paper Fiber 1024.3 Biological Degradation of Paper 1044.4 Wet-Strength Papers 1044.4.1 Major Categories of Wet-Strength Papers 1074.4.1.1 Urea-Formaldehyde B-stage Derivatives 1074.4.1.2 Melamine-Formaldehyde Cationic Colloids and Derivatives 1094.4.1.3 Polyamide-Polyamine-Epichlorohydrin (PPE) Resins 1104.4.2 Overview of Wet-Strength Resins 1104.5 Sustainable Materials for Paper Coating for Packaging Applications 1124.6 Concluding Remarks 117Problem Set for Chapter 4 117References 1185 Glass 1215.1 Advantages of Glass 1215.2 Disadvantages of Glass 1225.3 Glass Chemistry 1225.3.1 Composition 1225.3.2 Glass Making Process 1235.3.2.1 Common Types of Glass and Modification Strategies 1245.3.2.2 Stability of Glass 1255.4 Chemical Corrosion 1265.4.1 Leaching 1265.4.2 Etching 1275.4.3 Weathering 1275.5 Physical Stability and Strength of Glass 1285.5.1 Strategies to Modify or Strengthen Glass 1295.6 Chemical Modification and/or Strengthening 1295.6.1 Strengthening via the Fused Salt Mixture Approach 1305.6.2 Thermal Strengthening or Toughening 1315.6.2.1 Recyclability of Glass 1315.7 Conclusions 132Problem Set 132References 1336 Degradation and Stabilization of Metals 1356.1 Benefits of Metals as Packaging 1356.2 Disadvantages of Metals as Packaging 1366.3 Basic Aspects of Metal Corrosion 1366.4 Elements Required for Corrosion 1386.4.1 Anodes and Cathodes 1386.4.2 Electrolyte (the Internal Circuit) 1396.4.3 Circuit 1406.5 Role of Liquid Water in Corrosion 1406.6 Methods for Protecting Metals Used in Packaging from Corrosion 1426.6.1 External Environment Protection 1426.6.2 Internal Environment Protection 1426.7 Structure of Tinplate and Tin-Free Steel 1446.8 Corrosion in Plain (Uncoated) Tin Cans 1466.8.1 Normal Detinning 1486.8.2 Rapid Detinning 1496.8.3 Partial Detinning and Pitting 1496.8.4 Pitting Only 1496.9 Corrosion in Lacquered Cans 1496.10 Effects of Products, Processing, and Storage 1526.10.1 Effects of Products 1526.10.2 Effects of Processing and Storage Conditions 1536.11 VCI Packaging Materials 1556.12 Corrosion of Aluminum 1576.13 Lacquer Coatings for Cans 1596.13.1 Bisphenol A (BPA) 1606.14 Concluding Remarks 162Problem Set for Chapter 6 162References 163Further Reading 1657 Solid Waste Issues 1677.1 Overview of Packaging Waste in U.S. Municipal Solid Waste 1677.1.1 Municipal Solid Waste 1677.1.2 Products Generated in MSW, 2018 1767.1.3 Materials Generated in MSW, 2018 1767.2 Disposal of Packaging Materials 1837.2.1 Landfills 1837.2.2 Incineration 1887.2.2.1 So, Which Is More Expensive, Landfilling or Incineration? 1897.2.3 Heavy Metals in Packaging – CONEG Model Toxics Law 1907.2.3.1 Heavy Metals 1907.2.3.2 Lead 1907.2.3.3 Cadmium 1907.2.3.4 Mercury 1907.2.3.5 Hexavalent Chromium 1917.2.3.6 Heavy Metals in Packaging 1917.3 Recovery 1947.3.1 Composting 1947.3.2 Composting Process 1987.4 Reuse and Waste Reduction 2017.4.1 Reuse 2017.4.2 Source Reduction 2037.5 Recycling 2047.5.1 Recycling – General 2047.5.2 Collection of Recyclables 2067.6 Motivation 2087.6.1 Convenience 2107.6.2 Education/Publicity 2127.6.3 Participation Rates Versus Diversion Rates 2127.6.4 Separation/Sorting 2137.7 MRFs 2137.8 Comparative Advantages and Disadvantages 2147.9 Concluding Remarks 215Problem Set for Chapter 7 215References 2178 Recycling of Metal and Glass 2258.1 Overview 2258.2 Metal Recycling 2268.2.1 Steel Recycling 2268.3 Open-Loop and Closed-Loop Recycling 2298.4 Steel Recycling Process 2298.4.1 Steel Cans Recycling Process 2298.5 Aluminum Recycling 2308.5.1 Aluminum Beverage Cans 2308.5.2 Other Aluminum Packaging 2328.5.3 Aluminum Packaging Recycling Amounts 2328.5.3.1 Aluminum Packaging Recycling Rates 2328.5.4 Eddy Current Separation 2338.6 Glass Recycling 2358.6.1 Glass Recycling in the United States 2358.6.2 Glass Packaging Recycling Amounts 2358.6.3 Glass Recycling Elsewhere 2368.6.4 Glass Recycling 2378.6.5 Steps Involved in Glass Recycling 2378.6.6 What is the Future of Glass? 2398.7 Summary 242Problem Set for Chapter 8 243References 2449 Paper and Paperboard Recycling 2479.1 Sorting Phase 2529.2 Processing Phase 2529.3 Processing Phase: Pulp Screening and Cleaning 2529.4 Processing Phase: Deinking 2539.5 Processing Phase: Refining, Color Stripping, and Bleaching 2539.6 Processing Phase: Papermaking 2539.7 Recyclable Versus Repulpable Paper 2549.8 Uses of Recycled Paper 2559.8.1 Paper Recycling in Europe and Other Areas 2579.9 Contamination Issues 2599.10 Concluding Remarks 263Problem Set for Paper Recycling 264References 26510 Plastics Recycling 26910.1 Introduction 26910.2 Plastic Recycling Rates 26910.3 Recycling of Plastics Packaging 27010.4 What Is the Impact of Impurities in Plastics Mechanical Recycling? 27810.5 United States Plastic Scrap Exports 27810.6 Plastic Recycling Elsewhere 28010.6.1 European Plastic Recycling Numbers 28010.7 Global Plastic Recycling Rates 28110.8 CO2 Footprint of Different Ways of Plastic Disposal 28210.9 Terminology in Plastic Recycling 28210.9.1 Postindustrial Versus Postconsumer Plastics 28210.9.2 Chemical Versus Mechanical Recycling 28310.9.3 Extraction Approach 28310.9.4 Pyrolysis 28410.9.5 Chemical Upcycling 28510.9.5.1 Challenges Associated with Plastics Recycling 28510.9.5.2 Prices of Recycled plastics as of October 2023 28510.10 Emerging Trends in Recycling 28610.10.1 Challenges in Mechanical Recycling of Plastics 28610.10.1.1 Path Forward to Solve this Problem 28610.10.2 Digital Watermarking 28610.10.3 Near IR sorting 28710.10.4 Monomaterials 28810.10.5 Moving Towards Fewer Plastics 28810.10.6 Additives for Mechanical Recycling 28810.10.7 Additives to Enhance Properties of Recycled Materials 28910.10.8 Flexible packaging 28910.10.9 Path Forward in Mechanical Recycling 28910.11 Trends in Chemical Recycling 28910.11.1 Depolymerization to Monomers 29010.11.2 Conversion of Plastic Waste into Petrochemicals (chemicals) 29010.11.3 Summary of the Plastic Recycling Landscape 29210.11.4 PET Recycling 29210.11.5 Chemical Recycling of PET 29310.11.6 Key Technologies/initiatives in PET (Polyesters) Chemical Recycling 29510.11.7 Challenges PET Chemical Recycling 29510.11.8 Polyurethanes 29610.11.9 Polystyrene 29610.11.10 Recycling of PE (HDPE, LDPE, LLDPE) 29710.11.11 Chemical Recycling of PE 29810.11.11.1 Catalytic pyrolysis 29810.11.12 Hydrocracking of Plastics 30010.11.12.1 Ongoing Research 30110.11.13 Polypropylene 30110.11.14 Gasification of Mixed Plastics to Syngas 30110.11.15 Use of Recycled Plastics in Food Packaging 30210.12 Concluding Remarks 309Problem Set for Chapter 10 309References 31211 Legal, Regulatory, EPR, and Green Design 32111.1 Introduction 32111.2 EU Packaging Directives 32211.2.1 EU Directive Amendment (2018/852) 32311.2.2 How Are the Recycling Rates Calculated? 32411.3 Extended Producer Responsibility (EPR) 32511.3.1 Historical Background of EPR 32611.3.2 What Are the Potential Benefits of EPR? 32711.3.3 Recycled Content 32811.3.3.1 Oregon 32811.3.3.2 California 32911.3.4 Plastic Bags 33011.3.5 Single-Use Plastics 33011.4 Green Design 33111.4.1 Problematic Materials and Their Alternatives 33111.4.1.1 U.S. Plastics Pact 33211.4.1.2 Three Key Targets of the U.S. Plastics Pact 33211.4.1.3 The Do’s of Recyclable and Compostable Packaging 33211.5 The Path Forward for Packaging Sustainability 33211.5.1 Emerging Packaging Trends and Technology 33211.6 Concluding Remarks 336Problem Set for Chapter 11 336References 337Further Reading 342Appendix 1: Solutions to Problem Sets 343Index 357