Issue 13, 2024

Selective oxidative devulcanization of hydrosilylation-cured silicone elastomers: enhanced circularity

Abstract

In commerce, silicone elastomers are typically cured by platinum-catalyzed hydrosilylation or radical induced crosslinking (high temperature vulcanization (HTV)), both of which lead to crosslinks comprised of 2 or 3 carbon fragments. Alternatively, room temperature vulcanization (RTV) utilizes catalyzed nucleophilic substitution to give elastomers with Si–O–Si crosslinks. At end of life, the best current recycling protocols use aggressive acid/base conditions to regenerate cyclic monomers and mixtures of crosslinkers/fillers, etc. Over longer time periods all three types of elastomers undergo acid-catalyzed depolymerization initiated by HBr derived from bromine. However, we report that oxidative de-crosslinking with bromine of the Pt-cured elastomers occurs in minutes to hours to regenerate long chain silicone polymers, terminated with SiOH groups. It is therefore possible to devulcanize Pt-cured elastomers in the presence of RTV elastomers and reuse the high molar mass materials directly in new RTV elastomers, avoiding complete depolymerization, and thereby increasing the circularity of silicones.

Graphical abstract: Selective oxidative devulcanization of hydrosilylation-cured silicone elastomers: enhanced circularity

Supplementary files

Article information

Article type
Paper
Submitted
31 Dec 2023
Accepted
24 Feb 2024
First published
26 Feb 2024

Polym. Chem., 2024,15, 1310-1317

Selective oxidative devulcanization of hydrosilylation-cured silicone elastomers: enhanced circularity

M. E. Noman, M. K. Bayo, Y. Chen and M. A. Brook, Polym. Chem., 2024, 15, 1310 DOI: 10.1039/D3PY01431B

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