Improved ablative resistance and flexibility of silicone rubber modified by zirconium-containing ceramic precursor

Abstract

Aerospace application environment has posed great challenges to the ablation resistant silicone-rubber-based thermal protection materials, as the strength of char layer is the key factor of the ablation resistance. In the present work, through sol-gel method, vinyl-containing zirconium silicone oil (VZSO) was synthesized and introduced as the Zr-containing precursor into silicone rubber (SR) by hydrosilylation. In contrast to pure SR, the tensile strength and elongation at break increased by up to 63.83 % and 59.08 %, respectively, exhibiting obviously improved flexibility, which is beneficial for the adaptability to large load deformation. Most importantly, for thermal protective properties, mass ablation rate and charring rate decreased by up to 15.91 % and 38.21 %, respectively. During ablation, VZSO-modified SR could in-situ form tetragonal ZrO₂ (t-ZrO₂) to strengthen the char layer. With high-amount addition of VZSO, the stable and coherent char layer could resist the damage from inner pyrolysis gas and erosion from outer heat flux during ablation. This work proposes an effective strategy for the fabrication of high-performance silicon-rubber-based flexible ablation materials, potential to be employed as thermal protective coatings to protect spacecraft from serious service environments.