Recycling Silicone-Based Materials: An Overview of Methods

Abstract

Since the early 1800s, siloxane has been an industrial staple due to its remarkable structure, but even though there are many benefits for using siloxanes, there are significant environmental implications, one of which being the lack of recyclability. As the first step to polymerization or the depolymerization of polymers, the scission of the silicone bond is essential. While condition-specific reactions investigating what triggers polymerization have been extensively studied, traditional synthesis methods are unfortunately not ideal due to their high cost and detrimental release of greenhouse gases. Since the 1950s, several studies have related to rupturing the siloxane bond, including hydrolysis, catalytic depolymerization, thermal depolymerization, and radical extractions. This work has resulted in new polymers, cyclics, and monomeric silanes. However, only a few studies have focused on how to build new silicone-based materials from the primary siloxane cyclic forms. Thus, more investigation into better methods for recycling siloxanes is needed. This chapter summarizes and categorizes the published data on the degradation and depolymerization of polysiloxanes based on their reaction temperature up to July 2021.