Degradation, Stabilization, and Recycling of Packaging Materials

Preface xiii 1 Introduction 1 1.1 General Introduction 2 1.2 What Are Some Ideal Properties of Packaging? 2 1.3 Liquid Resistance and Barrier Properties 3 1.4 End-of-Life (EoL) Outcomes 4 1.5 Life-Cycle Assessment (LCA) and Techno-Economic Analysis (TEA) 4 1.6 Open-Looped Versus Closed-Loop Processes 5 1.7 Recycling 6 1.8 Biodegradable and Compostable Packaging 7 1.9 Concluding Remarks 7 References 8 2 Plastics 11 2.1 Introduction 11 2.2 How Are Polymers Named? 12 2.2.1 Classification of Polymers 12 2.2.1.1 Classification Based on the Polymer Structure 12 2.2.1.2 Classification Based on the Mechanism 13 2.2.1.3 Classification Based on the Source 13 2.2.1.4 Classification Based on Cost and Performance 14 2.2.1.5 Classification Based on Thermal Behavior 15 2.3 Molecular Architecture 15 2.3.1 Homopolymers and Copolymers 16 2.3.2 Polymer Molecular Weights 16 2.4 Polymer Characterization Techniques 19 2.4.1 Nuclear Magnetic Resonance Spectroscopy 20 2.4.2 Size Exclusion Chromatography 22 2.4.3 Viscosity 23 2.5 Microscopy Techniques 24 2.6 Physical State of a Polymer 24 2.7 Thermal Transitions 26 2.8 Mechanical Properties 27 2.9 Degradation of Polymers/Plastics 28 2.9.1 Overview 28 2.9.2 Impact of Degradation on Polymer Properties 29 2.10 Wanted Versus Unwanted Degradation in Polymers 29 2.10.1 Unwanted/Undesirable Degradation 29 2.10.2 Wanted/Desirable Degradation 30 2.11 Do all Polymers Degrade at the Same Rate? 31 2.11.1 How Can We Know if a Polymer Is Stable or not Against a Particular Degradation Environment? 31 2.12 Types of Polymer Degradation 32 2.12.1 Thermal Degradation 33 2.12.1.1 The Chemistry of Thermal Degradation 35 2.12.1.2 Some Polymers Degrade by Unzipping and Others by Random Scission 38 2.12.2 Oxidative Degradation 43 2.12.3 Photodegradation 51 2.12.4 Chemical Degradation 56 2.12.4.1 Hydrolysis 57 2.12.4.2 Environmental Stress Cracking 58 2.12.4.3 Other Chemical Reactions 59 2.12.4.4 Summary of Chemical Degradation Susceptibilities of Various Polymers 59 2.12.5 Mechanical Degradation 61 2.13 Methods for Studying Polymer Degradation 62 2.13.1 Weathering 63 2.13.2 Thermal Degradation 64 2.13.3 Photochemical Degradation 64 2.13.3.1 Change in Molecular Weight 64 2.14 Stabilization of Polymers 65 2.14.1 Antioxidants 65 2.14.1.1 Chain-breaking Electron Acceptors (CB-A Antioxidants) 66 2.14.1.2 Chain-breaking Electron Donors (CB-D Antioxidants) 68 2.14.2 Peroxide Decomposers 71 2.14.2.1 Stoichiometric Peroxide Decomposers (PD-S) 72 2.14.2.2 Catalytic Peroxide Decomposers (PD-C) 73 2.14.3 Metal Deactivators (MDs) 73 2.14.3.1 UV Light Absorbers and Other Light Stabilizers 74 2.14.3.2 UV Light Absorbers (UVA) 74 2.14.4 Quenchers of Photo-excited States 75 2.14.5 Special Stabilizers 77 2.14.6 Drawbacks of Stabilizers 78 2.15 Summary 82 Problem Set 82 References 83 3 Wood 87 3.1 Introduction 87 3.2 Wood Degradation 87 3.2.1 Weathering 88 3.2.1.1 Effects of Various Influences on Weathering 89 3.2.1.2 Effects of Wood Composition 89 3.3 Chemical Degradation 94 3.4 Biological Decomposition (Decay) 94 Problem Set 97 References 97 4 Paper Degradation and Stabilization 99 4.1 Introduction 99 4.2 Durability and Permanence 100 4.2.1 Quality of Paper Fiber 102 4.3 Biological Degradation of Paper 104 4.4 Wet-Strength Papers 104 4.4.1 Major Categories of Wet-Strength Papers 107 4.4.1.1 Urea-Formaldehyde B-stage Derivatives 107 4.4.1.2 Melamine-Formaldehyde Cationic Colloids and Derivatives 109 4.4.1.3 Polyamide-Polyamine-Epichlorohydrin (PPE) Resins 110 4.4.2 Overview of Wet-Strength Resins 110 4.5 Sustainable Materials for Paper Coating for Packaging Applications 112 4.6 Concluding Remarks 117 Problem Set for Chapter 4 117 References 118 5 Glass 121 5.1 Advantages of Glass 121 5.2 Disadvantages of Glass 122 5.3 Glass Chemistry 122 5.3.1 Composition 122 5.3.2 Glass Making Process 123 5.3.2.1 Common Types of Glass and Modification Strategies 124 5.3.2.2 Stability of Glass 125 5.4 Chemical Corrosion 126 5.4.1 Leaching 126 5.4.2 Etching 127 5.4.3 Weathering 127 5.5 Physical Stability and Strength of Glass 128 5.5.1 Strategies to Modify or Strengthen Glass 129 5.6 Chemical Modification and/or Strengthening 129 5.6.1 Strengthening via the Fused Salt Mixture Approach 130 5.6.2 Thermal Strengthening or Toughening 131 5.6.2.1 Recyclability of Glass 131 5.7 Conclusions 132 Problem Set 132 References 133 6 Degradation and Stabilization of Metals 135 6.1 Benefits of Metals as Packaging 135 6.2 Disadvantages of Metals as Packaging 136 6.3 Basic Aspects of Metal Corrosion 136 6.4 Elements Required for Corrosion 138 6.4.1 Anodes and Cathodes 138 6.4.2 Electrolyte (the Internal Circuit) 139 6.4.3 Circuit 140 6.5 Role of Liquid Water in Corrosion 140 6.6 Methods for Protecting Metals Used in Packaging from Corrosion 142 6.6.1 External Environment Protection 142 6.6.2 Internal Environment Protection 142 6.7 Structure of Tinplate and Tin-Free Steel 144 6.8 Corrosion in Plain (Uncoated) Tin Cans 146 6.8.1 Normal Detinning 148 6.8.2 Rapid Detinning 149 6.8.3 Partial Detinning and Pitting 149 6.8.4 Pitting Only 149 6.9 Corrosion in Lacquered Cans 149 6.10 Effects of Products, Processing, and Storage 152 6.10.1 Effects of Products 152 6.10.2 Effects of Processing and Storage Conditions 153 6.11 VCI Packaging Materials 155 6.12 Corrosion of Aluminum 157 6.13 Lacquer Coatings for Cans 159 6.13.1 Bisphenol A (BPA) 160 6.14 Concluding Remarks 162 Problem Set for Chapter 6 162 References 163 Further Reading 165 7 Solid Waste Issues 167 7.1 Overview of Packaging Waste in U.S. Municipal Solid Waste 167 7.1.1 Municipal Solid Waste 167 7.1.2 Products Generated in MSW, 2018 176 7.1.3 Materials Generated in MSW, 2018 176 7.2 Disposal of Packaging Materials 183 7.2.1 Landfills 183 7.2.2 Incineration 188 7.2.2.1 So, Which Is More Expensive, Landfilling or Incineration? 189 7.2.3 Heavy Metals in Packaging – CONEG Model Toxics Law 190 7.2.3.1 Heavy Metals 190 7.2.3.2 Lead 190 7.2.3.3 Cadmium 190 7.2.3.4 Mercury 190 7.2.3.5 Hexavalent Chromium 191 7.2.3.6 Heavy Metals in Packaging 191 7.3 Recovery 194 7.3.1 Composting 194 7.3.2 Composting Process 198 7.4 Reuse and Waste Reduction 201 7.4.1 Reuse 201 7.4.2 Source Reduction 203 7.5 Recycling 204 7.5.1 Recycling – General 204 7.5.2 Collection of Recyclables 206 7.6 Motivation 208 7.6.1 Convenience 210 7.6.2 Education/Publicity 212 7.6.3 Participation Rates Versus Diversion Rates 212 7.6.4 Separation/Sorting 213 7.7 MRFs 213 7.8 Comparative Advantages and Disadvantages 214 7.9 Concluding Remarks 215 Problem Set for Chapter 7 215 References 217 8 Recycling of Metal and Glass 225 8.1 Overview 225 8.2 Metal Recycling 226 8.2.1 Steel Recycling 226 8.3 Open-Loop and Closed-Loop Recycling 229 8.4 Steel Recycling Process 229 8.4.1 Steel Cans Recycling Process 229 8.5 Aluminum Recycling 230 8.5.1 Aluminum Beverage Cans 230 8.5.2 Other Aluminum Packaging 232 8.5.3 Aluminum Packaging Recycling Amounts 232 8.5.3.1 Aluminum Packaging Recycling Rates 232 8.5.4 Eddy Current Separation 233 8.6 Glass Recycling 235 8.6.1 Glass Recycling in the United States 235 8.6.2 Glass Packaging Recycling Amounts 235 8.6.3 Glass Recycling Elsewhere 236 8.6.4 Glass Recycling 237 8.6.5 Steps Involved in Glass Recycling 237 8.6.6 What is the Future of Glass? 239 8.7 Summary 242 Problem Set for Chapter 8 243 References 244 9 Paper and Paperboard Recycling 247 9.1 Sorting Phase 252 9.2 Processing Phase 252 9.3 Processing Phase: Pulp Screening and Cleaning 252 9.4 Processing Phase: Deinking 253 9.5 Processing Phase: Refining, Color Stripping, and Bleaching 253 9.6 Processing Phase: Papermaking 253 9.7 Recyclable Versus Repulpable Paper 254 9.8 Uses of Recycled Paper 255 9.8.1 Paper Recycling in Europe and Other Areas 257 9.9 Contamination Issues 259 9.10 Concluding Remarks 263 Problem Set for Paper Recycling 264 References 265 10 Plastics Recycling 269 10.1 Introduction 269 10.2 Plastic Recycling Rates 269 10.3 Recycling of Plastics Packaging 270 10.4 What Is the Impact of Impurities in Plastics Mechanical Recycling? 278 10.5 United States Plastic Scrap Exports 278 10.6 Plastic Recycling Elsewhere 280 10.6.1 European Plastic Recycling Numbers 280 10.7 Global Plastic Recycling Rates 281 10.8 CO2 Footprint of Different Ways of Plastic Disposal 282 10.9 Terminology in Plastic Recycling 282 10.9.1 Postindustrial Versus Postconsumer Plastics 282 10.9.2 Chemical Versus Mechanical Recycling 283 10.9.3 Extraction Approach 283 10.9.4 Pyrolysis 284 10.9.5 Chemical Upcycling 285 10.9.5.1 Challenges Associated with Plastics Recycling 285 10.9.5.2 Prices of Recycled plastics as of October 2023 285 10.10 Emerging Trends in Recycling 286 10.10.1 Challenges in Mechanical Recycling of Plastics 286 10.10.1.1 Path Forward to Solve this Problem 286 10.10.2 Digital Watermarking 286 10.10.3 Near IR sorting 287 10.10.4 Monomaterials 288 10.10.5 Moving Towards Fewer Plastics 288 10.10.6 Additives for Mechanical Recycling 288 10.10.7 Additives to Enhance Properties of Recycled Materials 289 10.10.8 Flexible packaging 289 10.10.9 Path Forward in Mechanical Recycling 289 10.11 Trends in Chemical Recycling 289 10.11.1 Depolymerization to Monomers 290 10.11.2 Conversion of Plastic Waste into Petrochemicals (chemicals) 290 10.11.3 Summary of the Plastic Recycling Landscape 292 10.11.4 PET Recycling 292 10.11.5 Chemical Recycling of PET 293 10.11.6 Key Technologies/initiatives in PET (Polyesters) Chemical Recycling 295 10.11.7 Challenges PET Chemical Recycling 295 10.11.8 Polyurethanes 296 10.11.9 Polystyrene 296 10.11.10 Recycling of PE (HDPE, LDPE, LLDPE) 297 10.11.11 Chemical Recycling of PE 298 10.11.11.1 Catalytic pyrolysis 298 10.11.12 Hydrocracking of Plastics 300 10.11.12.1 Ongoing Research 301 10.11.13 Polypropylene 301 10.11.14 Gasification of Mixed Plastics to Syngas 301 10.11.15 Use of Recycled Plastics in Food Packaging 302 10.12 Concluding Remarks 309 Problem Set for Chapter 10 309 References 312 11 Legal, Regulatory, EPR, and Green Design 321 11.1 Introduction 321 11.2 EU Packaging Directives 322 11.2.1 EU Directive Amendment (2018/852) 323 11.2.2 How Are the Recycling Rates Calculated? 324 11.3 Extended Producer Responsibility (EPR) 325 11.3.1 Historical Background of EPR 326 11.3.2 What Are the Potential Benefits of EPR? 327 11.3.3 Recycled Content 328 11.3.3.1 Oregon 328 11.3.3.2 California 329 11.3.4 Plastic Bags 330 11.3.5 Single-Use Plastics 330 11.4 Green Design 331 11.4.1 Problematic Materials and Their Alternatives 331 11.4.1.1 U.S. Plastics Pact 332 11.4.1.2 Three Key Targets of the U.S. Plastics Pact 332 11.4.1.3 The Do’s of Recyclable and Compostable Packaging 332 11.5 The Path Forward for Packaging Sustainability 332 11.5.1 Emerging Packaging Trends and Technology 332 11.6 Concluding Remarks 336 Problem Set for Chapter 11 336 References 337 Further Reading 342 Appendix 1: Solutions to Problem Sets 343 Index 357