In-situ formation of a micro/nano-scale phenolic–PDMS char-forming network for synergistically enhancing silicone rubber mechanical and ablative performance

Silicone rubber (SR) has attracted considerable attention as a flexible ablative material due to its excellent heat resistance and thermal insulation properties. However, its low mechanical strength and tendency to swell and pulverize under ablation conditions inhibit the formation of a robust char layer, limiting applications in extreme high-temperature environments. In this work, we designed a series of cross-linkers based on allyl phenolic resin (APR) and constructed a rigid-flexible balance APR-PDMS micro/nano bicontinuous char-forming network within the SR matrix, synergistically enhancing both mechanical properties and char-forming ability. The modified SR (PTRs) achieved a tensile strength of up to 4.88 MPa (a 597 % increase over SR) along with a char yield of 16 %, compared to 0 % for SR. At high temperatures, the APR-PDMS network spontaneously forms a robust and thermally insulating micro/nano-porous char layer induced by cyclic siloxane gases generated during pyrolysis, with a thermal conductivity as low as 0.0418 W/(m·K). The linear and mass ablation rates of PTRs-based composites were as low as 0.152 mm/s and 0.074 g/s, respectively, representing reductions of 34.5 % and 18.9 % compared to SR-based ablative materials. This work provides an innovative design strategy for developing high-performance flexible SR-based ablative materials.