Chapter 15 - Recyclable thermoset polymers: beyond self-healing

Abstract

Of the 78 million tons of plastic produced annually, only 14% are recycled, with a scant 2% used in closed-loop recycling processes, and the remaining 72% ending up in landfills or accumulating in the environment. As landfill space is becoming limited and expensive, and with the decade-, century-, or even millennia-long biodegradation timelines of various plastics, recycling plastics becomes a more important environmental and economical solution to manage plastic waste streams. This chapter provides a brief review in recent developments in recyclable thermosets using chemical approach with the related chemistry, recycling techniques, related modeling studies, and applications. It first outlines the current progress on recyclable thermosets based on degradable networks and then focuses on polymers using covalent adaptable network or with dynamic chemistries. The latter is often used for self-healing. Typical chemistries implied for producing these polymers are elaborated. Several promising thermoset recycling techniques based on dynamic chemistries are highlighted. Modeling efforts that enhance the understanding of covalent adaptable network behaviors during processing and recycling are also evaluated. Finally, some recent examples of recyclable thermoset-based applications and their future outlooks are discussed.