A Phosphazene-Silane hybrid crosslinker for room temperature vulcanized silicone rubber: Synthesis, structure and performance enhancement

Room temperature vulcanized silicone rubber (RTV) crosslinked with conventional silane agents often suffers from limited thermal stability and mechanical properties. To address this issue, a novel phosphazene–silane hybrid crosslinking agent (HC-PD-KH) was synthesized from a phosphazene derivative and 3-glycidyloxypropyltrimethoxysilane (KH-560) via epoxy ring-opening reaction. HC-PD-KH was used as a crosslinking agent to prepare RTV with hydroxy terminated polydimethylsiloxane (PDMS) matrix in the presence of an organotin catalyst. Comprehensive characterization revealed remarkable performance improvements: TGA showed significantly enhanced thermal stability compared with KH-560 systems, the 10% weight loss temperature (T₁₀) rose from 385.7 °C to 444.5 °C, the char yield at 800 °C rose dramatically from 1.2% to 11.4%; DMA and tensile tests demonstrated higher damping properties, tensile strength and modulus: the tensile strength and elongation at break reached 1.26 MPa and 200%; water contact angle measurements indicated improved hydrophobicity, with the water contact angle increasing from 93.5° to 103.4°. These enhancements are attributed to the rigid backbone of phosphazene rings and phenyl groups, the contribution of polar N H moieties, and the uniform dispersion of HC-PD-KH within the silicone matrix. This study provides a promising strategy for the molecular design and crosslinking of high-performance RTV.