National Academies Press: OpenBook

Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities (2023)

Chapter: Appendix J: Overview of Plastics by Resin Identification Code (RIC)

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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Suggested Citation:"Appendix J: Overview of Plastics by Resin Identification Code (RIC)." National Academies of Sciences, Engineering, and Medicine. 2023. Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities. Washington, DC: The National Academies Press. doi: 10.17226/27172.
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Appendix J Overview of Plastics by Resin Identification Code (RIC) RIC 1: POLYETHYLENE TEREPHTHALATE (PET OR PETE) • Properties:   Tough and strong.  Clear and good barrier properties. Can make optically smooth bottle sidewalls.  High melting point (>225°C to 255°C). Products usually crystalline.  Relatively high service temperature (150°C/302°F when crys- tallized) (glass transition temperature 73°C/163°F).  At room temperature, good chemical resistance.  Sinks in water. • Uses:  About two-thirds used for filament and staple fiber for apparel, carpet, and furnishing.  About one-third used for food and non-food bottles, cups, and thermoforms.  Also used for films (including Mylar films), strapping, and rope. • Recycle:  2018 U.S. post-consumer recycling rate for PET bottles and jars was 29.1 percent.  18.5 percent recycling rate overall for all PET (PET carpet sometimes recycled). 367

368 RECYCLED PLASTICS IN INFRASTRUCTURE  Recycled PET used for food and non-food containers, carpet, apparel, strapping. • Production volume, consumed in the United States:   Per the U.S. Environmental Protection Agency (USEPA), 5.290 million tons, 14.8 percent of all plastics.  • Comments:   Of the first six polymer types, this is the only condensation polymer.  Can be quantitatively depolymerized to monomers.  Recycle can be repolymerized as a solid (no need to melt).  Bottle PET actually a copolymer. Other copolymers often not PET.  In spite of name, not chemically related to polyethylene.  Hygroscopic and must be desiccant-dried before melting or PET degrades.  Recycled PET widely included in food and beverage packaging, which is mandated in several state laws (California, Washing- ton, New Jersey) RIC 2: HIGH-DENSITY POLYETHYLENE (HDPE)  • Properties:   Tough and strong.  White (non-clear) and good water barrier properties, fair gas barrier properties.  Modest melting point (131°C/268°F). Crystalline.  Modest service temperature (71°C/160°F).  At room temperature, good chemical resistance.  Floats in water. • Uses:  Bottles, caps, bags, pipe, geomembrane, toys, house wrap. • Recycle:  2018 U.S. post-consumer recycling rate for HDPE packaging was 14.8 percent, 8.9 percent recycling rate overall for all HDPE.  Recycled HDPE packaging used for pipe and new bottles. • Production volume, consumed in the United States:   Per USEPA, 6,380 million tons, 17.7 percent of all plastics.  • Comments:   An addition polymer, not chemically related to PET. An olefinic polymer.  Can be depolymerized by pyrolysis to small chemicals.

APPENDIX J 369  Recycled pellets cannot be repolymerized.  Bottle HDPE either natural (no copolymer) or copolymer (usu- ally colored), natural and copolymer are interchangeable.  Need not be desiccant-dried before melting.  Subject to state mandates for recycled content in packaging. Limited approvals by U.S. Food and Drug Administration (FDA) for recycled HDPE in food contact. RIC 3: POLYVINYL CHLORIDE (PVC) • Properties:   Neat PVC is brittle, toughened and made flexible by plasticiz- ers and other additives, often to levels of 40 percent.  Can be clear and fair barrier properties.  Always amorphous, no fixed melting point.  Processing temperature 140°C/284°F to 185°C/365°F  Relatively low service temperature (60°C/140°F).  At room temperature, excellent chemical resistance.  Sinks in water.  Does not support flames. • Uses:  Windows and siding, conduit, pipe, gutters, furniture, bottles, flooring, toys, wire insulation, and health care. • Recycle:  2018 U.S. post-consumer recycling rate for PVC was negligible. • Production volume, consumed in the United States:   Per USEPA, 0.84 million tons, 2.4 percent of all plastics.  • Comments:   An addition polymer.  Presence of corrosive chlorine makes unwelcome for pyroly- sis.  Recycled pellets cannot be repolymerized.  PVC needs stabilizers; lead was used, which makes old PVC unwanted for recycling.  Need not be desiccant-dried before melting.  Subject to state mandates for recycled content in packaging. No approvals by FDA for recycled PVC in food contact.  Globally, third most produced plastic after polyethylene and polypropylene.

370 RECYCLED PLASTICS IN INFRASTRUCTURE RIC 4: LOW-DENSITY POLYETHYLENE (LDPE) AND LINEAR LOW- DENSITY POLYETHYLENE (LLDPE) • Properties:   Almost always a flexible film. Stretchable, unlike crystalline HDPE films.  Clear, good water barrier properties, and fair gas barrier properties.  Modest processing temperature (160°C/320°F to 220°C/428°F).  Amorphous.  Modest service temperature (71°C/160°F).  At room temperature, good chemical resistance except for halogenated hydrocarbons, such as chloroform.  Floats in water. • Uses:  Films, stretch wrap, flex pipe, bags, cable covering, pouches, lids, and laminates. • Recycle:  2018 U.S. post-consumer recycling rate for LLDPE/LDPE packaging was 9.9 percent, 4.3 percent recycling rate overall for all LLDPE/LDPE. • Production volume, consumed in the United States:   Per USEPA, 8,590 million tons, 24 percent of all plastics.  • Comments:   An addition polymer, not chemically related to PET. An olefinic polymer.   Different in structure than HDPE.   Can be depolymerized by pyrolysis to small chemicals, includ- ing ethylene.   Recycled pellets cannot be repolymerized. Small-chemical eth- ylene can be repolymerized.  Lacks collection infrastructure for collection from public for recycling.  Need not be desiccant-dried before melting.  Subject to state mandates for recycled content in packaging. Very limited approvals by FDA for recycled LDPE in food contact. RIC 5: POLYPROPYLENE (PP) • Properties:   Tough and strong. Resists fatigue failure (“living hinge”).

APPENDIX J 371  Clear and good water barrier properties, fair gas barrier properties.  High melting point (164°C/327°F). Can be crystalline or amorphous.  Robust service temperature (can be 82°C/180°F).  At room temperature, good chemical resistance.  Floats in water. • Uses:  Injection moldings (toys, caps, containers) and extrusions (bot- tles, films [both oriented and unoriented], labels, filaments, and non-wovens, carpet). • Recycle:  2018 U.S. post-consumer recycling rate for PP packaging was 2.7 percent, 0.6 percent recycling rate overall for all PP. • Production volume, consumed in the United States:   Per USEPA, 8,150 million tons, 22.8 percent of all plastics.  • Comments:   An addition polymer. An olefinic polymer.  A highly versatile plastic that can be used as a replacement for other plastics for many applications.  Not the most inexpensive plastic or the most chemically stable without additives.  Can be depolymerized by pyrolysis to small chemicals.  Recycled pellets cannot be repolymerized. Small-chemical pro- pylene can be repolymerized.  Need not be desiccant-dried before melting.  Subject to state mandates for recycled content in packaging. Limited approvals by FDA for recycled PP in food contact. RIC 6: POLYSTYRENE (PS) • Properties:  Clear, hard, and stiff. Brittle unless modified.  White (non-clear) and poor water and gas barrier properties.  Modestly high melting point (185°C/365°F to 240°C/464°F). Usually amorphous.  Modest service temperature (100°C/212°F).  Dissolves in many non-aqueous solvents.  Sinks in water. • Uses:  Packing dunnage, foams, containers, lids, bottles, trays, tum- blers, and disposable cutlery.

372 RECYCLED PLASTICS IN INFRASTRUCTURE • Recycle:  2018 U.S. post-consumer recycling rate for PS packaging was 3.6 percent, 0.9 percent recycling rate overall for all PS. • Production volume, consumed in the United States:   Per USEPA, 2,260 million tons, 6.3 percent of all plastics.  • Comments:   An addition polymer.  Can be depolymerized by pyrolysis to small chemicals, includ- ing styrene.   Recycled pellets cannot be repolymerized. Styrene from pyroly- sis can be repolymerized to PS.  Need not be desiccant-dried before melting.  Subject to state mandates for recycled content in packaging. Limited approvals by FDA for recycled PS in food contact. RIC 7: OTHER RESINS This resin category refers to other polymers, a blend of plastics, or multi- layers of materials.  • Properties:   Variable • Uses:  Variable • Recycle:  2018 U.S. post-consumer recycling rate for “Other resins” was 26.7 percent. (USEPA does not specify the plastics.) • Production volume, consumed in the United States:   Per USEPA, 4.160 million tons, 14.8 percent of all plastics.  • Comments:   Can include nylons, ABS, polyurethanes, and others.

Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities Get This Book
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In the U.S., most plastics waste is disposed in landfills, but a significant amount also ends up as litter on land, rivers, and oceans. Today, less than 10 percent of plastics waste is recycled in the U.S. annually. The use of recycled plastics in infrastructure applications has potential to help expand the market and demand for plastics recycling.

These are among the findings in TRB Special Report 347: Recycled Plastics in Infrastructure: Current Practices, Understanding, and Opportunities from the Transportation Research Board of the National Academy of Sciences, Engineering, and Medicine.

The report emphasizes that pursuing the recycling of plastics in infrastructure depends on goals, policy, and economics. To that end, life cycle economic and environmental assessments should be conducted to inform policies on plastics waste reuse.

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