Phosphazene derivative cross-linked liquid silicone rubber and its mechanical and thermal properties

It is still a challenge for liquid silicone rubber to meet the needs of aerospace and electronics in terms of mechanical and thermal properties. In this study, N₃P₃ [NH(CH₂)₃Si(OCH₂CH₃)₃]₆ (APESP), a phosphazene derivative containing multiple siliconethoxy groups was adopted as cross-linking agent to cure the condensed room temperature vulcanizing liquid silicone rubber (RTV-CLSR). The results show that APESP can effectively complete the curing process of condensed silicone rubber taking the place of tetraethyl orthosilicate (TEOS), and enhance the restriction of cross-linking point to molecular chains, thereby effectively improving the mechanical strength, thermal stability, and ablation resistance of SR. Compared with unmodified SR, the tensile strength of APESP modified SR increased by 272%, the elongation at break decreased slightly but still remained at 362%, and the mass residual rate at 800 °C significantly increased by 19.86% when 11 phr APESP was added. The linear ablation rate and mass ablation rate of SR were reduced to 0.239 mm·s⁻¹ and 0.095 g·s⁻¹, a decrease of 60.63% and 44.41%, respectively. This work may provide a new perspective for the application of liquid silicone rubber in the fields with high thermal performance requirements.