Preparation and Ablation Resistance of VMQ/PDPP Blended Composites

Rubber-based composites are widely used as ablative thermal protection materials in aerospace and defense, with performance demands continuously increasing. This work prepared a series of VMQ/PDPP composites by blending methyl vinyl silicone rubber (VMQ) with polyphosphazene elastomer (PDPP) and incorporating fillers including fumed silica, MoSi2, boron-containing phenolic resin (BPR), and a glass frit. Results indicated that tensile strength was significantly enhanced with increasing PDPP content. The optimal formulation SPMB-5 (VMQ/PDPP = 10/90) exhibited a tensile strength of 9.38 MPa, representing a 317% improvement over pure VMQ. This sample also demonstrated the lowest linear ablation rate of 0.062 mm/s and mass ablation rate of 0.054 g/s, corresponding to reductions of 20% and 24%, respectively, compared to pure VMQ. Microstructural analysis revealed that exposure to 1200 °C formed a multiphase ceramic structure composed of Mo4.8Si3C0.6 and SiC, which substantially improved the compactness, thermal stability and creep resistance of the char layer. Finite element simulations confirmed that PDPP incorporation reduced thermal stress from 1.12 MPa to 0.62 MPa, effectively suppressing stress concentration. This work elucidates the synergistic mechanism of multiphase ceramic formation and thermal stress regulation in enhancing ablation resistance, providing valuable guidance for developing advanced ablative materials.