| The properties of high-temperature ablative resistant are needed for the insulation material, since the temperature is up to 3000℃ in the combustion chamber of solid rocket. The silicone rubber based insulation material is a kind of advanced and high-performance insulation material because of its excellent anti-oxidative and anti-ablative.properties.Under the ablation process, silicone rubber based insulation material changed into ceramic layer with Si C, C and Si O2. It’s obviously that the ceramic layer is the key structure of anti-ablation of the insulation material. Howerver, the correlation between the linear ablative rate and the propeities of ceramic layer, which include the constituents and structure, has not been established, and the effects of precursors on the ceramic layer and on the linear ablative rates of insulation materials are lack of study. Meanwhile, these relationships are very important to optimize the formulations and performance of the insulation materials, and can be used to decrease the linear ablation rate.The effects of carbon-rich precursors(phenol aldehyde, precursor A and precursor B) and silicon-rich precursors(PCS, LPVCS and precursor C) on properties of ceramic layeer and silicon rubber based insulation material were studied in this paper. By changing the contents and species of the precursors, the linear ablative rates and properties of ceramic layer were adjusted. Then the correlations between the linear ablative rates and the propeities of ceramic layer were studied.The linear ablative rates of insulation materia ls decreased with addition of carbon-rich precursors. Meantime, they are incresaed that the ceramic ratio and the contents of the in-situ Si C in ceramic residue in tube furnace and in the ceramic layer formed under the oxygen-acetylene flame. The linear ab lative rate of the insulation material containing 14.6wt% A is the lowest, which is 0.112 mm·s-1, among the three species of carbon-based precursors. The linear ablative rates decreased as the contents of C and the in-situ Si C increased in ceramic layer formed under the oxygen-acetylene flame. It also decreased when the C/Si ratio increased and the contents of Si O2 decreased.With addition of silicon-rich precursors, the ceramic ratio in tube furnace and the content of in-situ Si C in the ceramic layer formed under the oxygen-acetylene flame increased. The insulation material containing 14.6wt% PCS gives the highest ceramic ratio in tube furnace and the highest content of in-situ Si C in ceramic layer. The insulation material containing 14.6wt% silicon resin has the lowest linear ablative rate, which is 0.115mm·s-1.Both the carbon-rich precursors and the silicon-rich precursors can increase the contents of in-situ Si C under the ablation process. The in-situ Si C contents of the insulation materials with carbon-rich precursors was higher than that of the insulation materrials with silicon-rich precursors in ceramic residue produced in tube furnace. However, the Si C contents of the insulation materials with carbon-rich precursors in the ceramic layer under the oxygen-acetylene flame have no significant difference with that of the insulation materrials containing silicon-rich precursors. The linear ablative rates can be obviously decreased by addition of carbon-rich precursors and the silicon resin. |
