硅橡胶基防热涂层动态烧蚀行为及机理研究

针对两种典型硅橡胶基防热涂层开展高温燃气流烧蚀实验，通过对烧蚀后涂层的宏观及微观形貌分析，探讨了其防隔热机理及烧蚀模型。研究结果表明：烧蚀后两种涂层均存在液态层、陶瓷层、热解层以及原始层；烧蚀过程中甲基苯基硅橡胶涂层主要发生主链“回咬”成环反应，导致树脂基体交联密度降低，力学性能下降，涂层外表面发生开裂，甲基乙烯基硅橡胶涂层则主要发生侧基交联反应，使树脂基体交联密度上升，促进涂层发生陶瓷化转变；热辐射、热容吸热、热解反应吸热以及热阻塞效应为四种主要的热耗散机制，质量损失产生的原因主要包括反应气体释放以及气动剪切力导致的机械剥蚀。

Study on Dynamic Ablative Behavior and Mechanism of Silicone Rubber Based Thermal Protective Coating#br#

Two typical silicone rubber based thermal protective coatings are investigated by high temperature gas flow experiments. The macroscopic morphology and microstructure after ablation are analyzed. Meanwhile, the ablation model and ablation mechanism of the silicone rubber based thermal protective coating are discussed. The results show that after ablation, both the two coatings have liquid layer, ceramic layer, pyrolysis layer and original layer; during the ablation process, the main chain “back biting” reaction plays a major role for the methyl phenyl silicone rubber, leading to the resin cross linking degree decrease and mechanical properties degradation, and resulting in bubbling and cracking occurring on the coating surface; as for the methyl vinyl silicone rubber, side group cross linking reaction plays an important role during the ablation process, leading to the resin cross linking degree increase, thus promoting the transformation of the silicon rubber from organic to inorganic. Thermal radiation, heat capacity absorbing heat, pyrolytic reaction absorbing heat and thermal blockage effects are four important endothermic mechanisms. The reason for the quality loss mainly includes two aspects, the first one is the release of reaction gas and the second one is the mechanical erosion caused by shear force.