Research On Preparation And Performance Of Propellant Coating Materials

The solid propellant,as the power source of the weapon,contains high energy and generates a large amount of high temperature,high pressure,and high speed gas during the combustion process.In order to alleviate the thermal erosion effect of the combustion gas products on the engine case,during the propellant combustion the engine is guaranteed the shell has its structural integrity,and the requirements for the ablation resistance,erosion resistance and heat insulation are proposed corresponding to the coating material used between the engine casing and the propellant grains.This article explores an ablation-resistant coating material based on EVA,LDPE,and EPDM with heat shrinkage characteristics in addition to the traditional nitrile rubber,EPDM,and silicone rubber coating systems.This article analyzes the way to achieve the ablation resistance of the coating material.Unlike the traditional polymer flame retardant requirements,the application environment of the propellant coating material is more severe.At a high temperature of more than 3000℃,it is subjected to thermal erosion and thermal scour by high pressure and high-speed airflow,so the realization of ablation resistance is mainly based on the carbonaceous layer generated by the material at high temperature.The coating material is pyrolyzed under the circumstance of high-temperature gas flow,generates the char with physical and chemical stability.And the purpose of the flame retardant filler is to make the material be thermally decomposed into elemental carbon as much as possible under high temperature conditions,and the structure of the char formed is more dense,and the thermal stability is better,and with certain strength.It can still maintain certain integrity under high-speed airflow.In this paper,the effects of phosphor-nitrogen flame retardants,silicon-flame retardants,carbon forming agents and aramid fibers on the ablative properties of coating materials were studied.The synergistic effect of multiple components is used to achieve optimal effect of the material’s ablation resistance,which is characterized by oxygen-acetylene ablation test and thermogravimetric analysis test.Among them,the flame retardant fillers with better performance are ammonium polyphosphate,silica white,barium phenolic resin,and aramid fiber.Content,in which 24 parts of ammonium polyphosphate,16 parts of silica white,6 parts of aramid fiber,and 16 parts of barium phenolic resin,the coating material has the best ablation resistance,and its linear ablation rate is 0.086 mm/s.In this paper,a hybrid silicon material is prepared by heat-treating the silicone rubber under a specific atmosphere and a specific temperature.The hybrid silicon material is an organic and inorganic hybrid material,and the infrared spectrum indicates that the organic components contain methyl,vinyl,etc.The inorganic components are silicon dioxide,elemental carbon,and silicon carbide,which have good thermal stability.The residual weight reaches 88% when the temperature of the thermogravimetric test reaches 1000 ° C.The coating material prepared by adding it into the matrix material instead of silica white as a silicon-based flame retardant has higher compatibility due to the presence of organic components,and the elongation at break has been significantly improved by 82% to 231%;at the same time,due to the presence of elemental carbon and silicon carbide,the material’s ablation resistance is further improved,and the linear ablation rate reaches 0.053 mm/s,and the nitrogen of the char formed after the erosion is higher,the porosity of the char is lower,and the pore size is smaller,which makes the coating material have better resistance to thermal erosion under the circumstance of high temperature and high pressure airflow,so the performance of erosion resistance is better.