Ordered graphitized ceramic layer induced by liquid crystal epoxy resin in silicone rubber composites with enhanced ablation resistance performance

Highlights: • The average ablation rate was reduced significantly. • The liquid crystal led to more orderly graphitic carbon structures during pyrolysis. • The liquid crystal component increased the strength of the ceramic layers. • More holes generated could prevent the flame from spreading to deeper layers of the sample. In ablation-resistant silicone rubber composites, the strengths of the ceramic layers strongly affect the ablation rates of the materials, and the order of graphite carbon in the ceramic layers has an important impact on the strength of ceramic layers. In this study, a series of 4,4′-bis(3-(oxiran-2-ylmethoxy)benzyl)-1,1′-biphenyl(BER) modified silicone rubber composites were prepared to improve the order of graphite carbon in the ceramic layers of composites after ablation. The introduction of SiO₂ nanoparticles and carbon fibers as ablation fillers made the material ceramized and formed strong ceramic layers during the ablation process. Characterization of ablation performance shown that the 20BER composite exhibited the best ablation resistance performance: a linear ablation rate of 0.0464 mm/s and a mass ablation rate of 0.0500 g/s. Mechanical performance characterization shown that the 20BER sample also exhibited an excellent tensile strength of 2.013 MPa and a ceramic layer strength of 13.15 MPa. Raman measurement indicated that the addition of BER led to more orderly graphitic carbon structures during pyrolysis and increased the strength of ceramic layers. SEM, mercury intrusion and thermal conductivity measurements indicated that the pore volume, porosity and total pore area of ceramic layers with the BER component were all higher than the 0BER sample. The BER was proven to be an effective material which is beneficial to improve the ablation resistance and played an important role in the process of ceramization of the silicone rubber composites. These silicone rubber composites have the potential to be applied to the surface coating of aircraft.