Thermal and thermo-oxidative accelerated aging of fluorosilicone rubber

• Thermal oxidation of a filled crosslinked fluorosilicone rubber at temperatures ranging from 200 to 250 °C under air or inert atmosphere • Multiscale characterization of rubber by tensile tests, sol-gel analysis • Highlight of a significant amount of soluble chains characterized by GPC, TGA and 29 Si NMR • Discussion of the possible degradation mechanisms depending on external atmopshere The thermal and thermo-oxidative accelerated aging of commercial fluorosilicone rubber (FSR) has been investigated at 200, 220, and 250 °C under air and nitrogen with a focus on macromolecular changes during aging, specifically crosslinking and network scission development. Under nitrogen, chain scission is the primary macromolecular change, evidenced by an increased soluble fraction, higher swelling ratio in ethyl acetate, and decreased stiffness, characterized by tensile test data. In an oxidative environment, degradation behavior varied with temperature. At 200 °C and 250 °C, crosslinking dominated, while at 220 °C, scission and crosslinking contributed nearly equally. Under all conditions, the soluble fraction increased over time. Analyses of this fraction using 29 Si NMR and GPC revealed mechanistic explanations for the scission process under air that have been summarized. The proposed chemical mechanisms offer a comprehensive understanding of the degradation pathways of FSR at high temperatures under oxidative conditions.