A double-decker silsesquioxane of norbornene and performance of crosslinking reactive modified EPDM ablation resistance composites

•A novel Double-Decker Silsesquioxane (DN-DDSQ) of norbornene was designed and synthesized for crosslinking reactive with EPDM.•The incorporation of DN-DDSQ into EPDM molecular chains through chemical cross-linked modification can greatly facilitate the mechanical and ablation resistance performance of EPDM and aramid fiber-reinforced EPDM.•EPDM ablation resistance composites modified by DN-DDSQ can promote the in-situ transformation of the SiC at lower temperature and further thermal decomposition at higher temperature, absorbing more energy to resist the oxyacetylene torch resulting in improved ablation performance.