Ablation resistance of ethylene propylene diene monomer insulation materials reinforced with liquid hyperbranched polycarbosilane coated aramid fibers

As a type of filler with excellent performance, fibers can effectively enhance the mechanical properties and ablation resistance of the EPDM insulation layer inside a solid rocket motor. However, an excessive amount of short-cut fibers can reduce the mechanical performance of the insulation layer. Therefore, in this work, a novel EPDM insulation material was reinforced by aramid fiber (AF) coated with liquid hyperbranched polycarbosilane (VHPCS) to improve the mechanical properties and ablation resistance of obtained composites by enhancing the interfacial properties between EPDM and AF as well as protecting the AF framework by in-situ transformation into a ceramic structure during ablation. The test results demonstrated a significant improvement in the ablation performance of the AF insulation materials coated with VHPCS. The linear ablation rate and mass ablation rate decreased by 22.67 and 11.67%, respectively. Furthermore, compared with the composites without VHPCS, the elongation at break was improved while maintaining the original tensile strength (60.60%). XRD and XPS analysis confirmed the presence of SiC formation in the carbon layer during ablation. Thermal analysis indicated that VHPCS increased the mass residual rate of the EPDM composites. Coating AF with VHPCS-modified EPDM increased the content of SiC structures on the carbon layer surface, effectively protecting the carbon layer structure and enhancing the ablation performance of the ceramicizable insulation.