Technical Paper Archive


This site contains all papers presented at Rubber Division, ACS Technical Meetings from 2000-2018. Meetings prior to 2000 are incomplete and papers are added as they are digitized.


For older papers not listed here, please send your request, including Meeting Year, Title, Author, and Paper # to: cbrady@rubber.org


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Transforming Rubber and Rubber Composite Thermosets into Themoplastics: Dynamic Covalent Bonds Enable Sustainable Recycling of Traditionally Non-Recyclable Polymer Materials

E01 torkelson

Event: 200th Technical Meeting - Fall 2021
Location: Pittsburgh, PA
Date: October 05, 2021
Author: John Torkelson
Paper Number: E01

Price: $20.00

  • The production of conventional crosslinked polymers and their composites has been estimated at ~100 billion lb annually. Unfortunately, thermosets cannot be melt-reprocessed into moderate- to high-value products because permanent crosslinks prevent melt flow. Rubber tires are an important example; tires are disposed at a rate approaching 300 million per year in the USA alone, with major economic and sustainability losses because they are commonly landfilled or burned for energy. My research group has employed simple reactions to produce networks and network composites with dynamic covalent crosslinks that are robust at use conditions but allow for melt-state reprocessing at high temperature. We have developed two approaches that allow for melt-state reprocessing of addition-type polymer networks and network composites, including those synthesized directly from monomers and those synthesized from combined polymer and monomer with both containing carbon-carbon double bonds, similar to materials used in tire production. Both approaches allow for full crosslink density recovery after multiple reprocessing steps. We have also demonstrated the ability to make polyurethane (PU) elastomer networks and PU-like networks, from polyhydroxyurethane and polythiourethane, reprocessable with full recovery of crosslink density. An “Achilles heel” has been identified with regard dynamic covalent networks, i.e., such networks are subject to creep (strain over time when placed under stress) at elevated or even room temperature, which is often highly undesirable. We have successfully addressed this limitation in two ways, which we will discuss. Opportunities for moving dynamic covalent polymer networks from research to the circular economy will also be discussed.

    Papers from 200th Technical Meeting - Fall 2021

    Items from 200th Technical Meeting - Fall 2021