Converting commercial-grade silicone into a vitrimer using elemental sulfur

Abstract

The silicone industry is rapidly expanding due to the high demand for biocompatible materials exhibiting properties such as temperature and solvent resistence as well as flexibility. However, due to its heavily cross-linked structure, silicone is not repairable or easily recycled, resulting in a large quanitity of silicone waste. As a first step towards synthesising repairable commercial-grade silicone, we incorporated dynamic S–S cross-links through the addition of elemental sulfur. By partially intercepting the platinum-catalysed hydrosilylation process, that occurs during curing of commerical grade silicone, with a small amount of vulcanisation using sulfur, a vitrimeric material was formed. The success of integrating S–S cross-links was determined using SEM, elemental analysis, as well as SSNMR, FT-IR, and Raman spectroscopies. The physical and mechanical properties of the sulfur containing silicone was compared to the unmodified silicone through a comparsion of TGA, DSC, rheology, and contact angle measurements before and after the healing process. This research not only provides a sustainable pathway for the utilisation of sulfur, a byproduct of petroleum and gas refining, it also represents a significant advancement in the development of self-healing materials, aligning with the broader environmental and resource conservation goals in industrial applications.