Preparation of Robust Thermal Protection Silicone Rubber by Constructing Interconnected C–Si Hybrid IPNs

Flexible thermal protection materials are an important component of thermal protection systems. In order to obtain flexible thermal protection materials with excellent mechanical strength, adhesive strength, and ablation resistance, a novel bifunctional biphenyl-type epoxy (MNE) monomer with two epoxy groups and vinyl groups was synthesized and utilized to construct interconnected C–Si hybrid interpenetrating networks in silicone rubber. Benefiting from the formation of C–Si hybrid IPNs and the incorporation of polar groups and biphenyl units, when the content of MNE was 20% (MNE-20), the tensile strength, elongation at break, and bonding strength of MNE-20 were 2.44 MPa, 179%, and 1.98 MPa, respectively, which were 510% improved, 56% improved, and 519% improved compared to those of the pure PDMS. Meanwhile, the mass ablation rate of MNE-20 decreased to 0.019 g/s, 53.66% improved compared to that of pure PDMS, because pyrolysis gases were released across a broad temperature range and the quality of the pyrolysis carbon layer was significantly improved. This work provided a new strategy to design high-performance ablation-resistant elastomers, and the prepared materials have broad applications in fields such as aerospace sealing materials and high-temperature protective coatings.