Preparation And Properties Of Elasto-plastic Silicone For Thermal Protection Coating With High Shear Resistance

The new generation of spacecraft has higher maneuverability,and the thermal environment is more severe.The specific performance is that the heat flow of the aircraft body is higher and the time is longer.Therefore,the reliable thermal protection system has become one of the key technologies to determine the success or failure of the new generation of spacecraft.The thermal protective coating of silicone rubber has the characteristics of simple application,low cost and good thermal protection effect,which is especially suitable for the thermal protection of complex aerodynamic structure parts of spacecraft.However,the existing silicone rubber has chain degradation under high temperature,and the final product is loose silica powder,without mechanical strength,so it is necessary to develop a new thermal protective coating.In this paper,the preparation and properties of elasto-plastic silicone matrix were studied.At first,organsilicon intermediate was synthesized,which was chemically grafted with hydroxyl terminated polysiloxane under the action of catalyst.The synthesized products were characterized by Fourier transform infrared spectroscopy(FTIR),1H-NMR and GPC.The results showed that elasto-plastic silicone was successfully synthesized.The effects of synthesis conditions,such as solvent type,catalyst type and dosage,reaction temperature,etc.on the preparation of elasto-plastic silicone were investigated,and the appropriate reaction conditions were determined.The mechanical properties and thermal stability of elasto-plastic silicone Silicone were characterized by mechanical properties test,thermogravimetric analysis and muffle furnace ablation.The results show that compared with silicone rubber,elasto-plastic silicone has better thermal stability,smoother ablation morphology and greatly improved mechanical properties.Secondly,the preparation and properties of the elasto-plastic silicone based heat-resistant coating were studied.The effect of a single filler on the mechanical properties of the elasto-plastic silicone Silicone and the ablation performance of muffle furnace was investigated,and the basic formula of the elasto-plastic silicone Silicone heat-resistance coating was determined.The results show that the tensile strength,elongation at break and ablation state of the coating are better than those of the coating.Finally,Flynn-wall-Ozawa method was used to calculate the apparent activation energy indifferent stages of the decomposition process of the elasto-plastic silicone.On this basis,the thermal degradation process of the elasto-plastic silicone was analyzed.The ablation structure of the thermal protective coating was characterized by SEM,EDS and FTIR,and the ablation mechanism was clarified.