Plastic waste is one of the most significant challenges facing the modern world. One possible approach is to develop new plastics that can be chemically recycled, rather than mechanically recycled. The new plastic products should be able to be decomposed on demand but must have mechanical stability throughout the lifetime of the materials. However, when decomposing polymeric materials to their reusable states (i.e. monomer or oligomers), the depolymerization mechanisms vary and impact the purity and quality of the reusable monomers, which makes even greater obstacles for chemical recycling. In addition, depolymerizing polymers often requires harsh conditions for complete depolymerization if the structures of polymers are intrinsically stable. As a first step to designing degradable and depolymerizable composites, we examine a crosslinked system of simple polyester with silica particles. The silica particles are surface modified with crosslinking agents and reacted with polyester oligomers to make composite films that can be degraded by triggering the breakage of the crosslinks between the polymers and particles, returning the system to a particle/oligomer mixture. Important to the design of resilient composites that are degradable on command is a selection of crosslinking chemistries. We modify the surface of silica particles with a variety of crosslinking agents and study the kinetics of crosslinking and degradation. Since understanding the conditions for degradation of plastics and their kinetics are significant for developing a robust material, we believe this approach will reveal a path to mechanically resilient, but chemically degradable plastics and lead to a path for a closed-loop recycling system.

Solid-state degradation of simple polyester composites under mild conditions

ACS Fall 2021

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