Preparation and properties of aerospace silicone rubber sealing materials

Silicone rubber has excellent elasticity and high and low temperature resistance, and is widely used as sealing material in the aerospace field. With the development of aerospace engineering, the problem of silicone rubber sealing is gradually prominent, so it is of great significance to the preparation and performance research of silicone rubber sealing material. Taking methyl vinyl silicone rubber for rubber raw rubber, first of all, by changing the vulcanizing agent and reinforcing filler, optimize the silicone rubber reinforcing structure control agent content formula, and then USES the Fe2O3, biomass graphene and carbon nanotubes to heat aging modification of silicone rubber, and USES the talcum powder, graphite powder and 26 type fluorine rubber to low permeability of modified silicone rubber. In the reinforcement study of silicone rubber sealing material, the influence of diisopropyl peroxide (DCP), silica black and structure control agent on mechanical properties and heat aging properties of silicone rubber were studied respectively. The results of DCP showed that with the addition of DCP from 0.4 PHR to 1.6 PHR, the tensile strength of samples aged at room temperature and 250℃×48h increased first and then decreased. The optimum addition of DCP is 1.0 PHR, and the tensile strength of the sample at room temperature and the tensile strength retention rate after aging can reach 7.66MPa and 64%. The results show that gas phase silica has the best reinforcing effect. The optimum filling amount of gas phase silica is 45phr, the tensile strength of the sample before aging and after aging at 250℃×48h can reach 7.66mpa and 4.87mpa, respectively, and the compression permanent deformation is 21%. The study of structural control agent shows that the composite of hydroxyl silicone oil/hexamethyldisilazane has better comprehensive properties. When the total amount of structural control agent is 9phr, the optimal ratio of hydroxyl silicone oil and hexamethyldisilazane is 1:1, the tensile strength of the vulcanized sample can reach 7.36MPa at room temperature, and the tensile strength retention rate of the sample after aging at 250℃×48h And elongation at break can reach 71% and 21% respectively. By comprehensive comparison, the best reinforcing formula of silicone rubber is: silicone rubber raw rubber 100phr, silica fume 45phr, hydroxyl silicone oil 4.5phr, hexamethyldisilazane 4.5phr,DCP1.0phr. The effects of Fe2O3, biomass graphene microsheets and carbon nanotubes on the properties of silicone rubber were studied. The results show that Fe2O3, biomass graphene microplates and carbon nanotubes can significantly enhance the thermal aging properties of silicone rubber. Compared with Fe2O3 and biomass graphene microsheets, carbon nanotubes have the best heat-resistant reinforcing effect. The optimal addition amount of carbon nanotubes is 0.9 PHR, and the tensile strength of the sample can reach 5.36MPa after aging at 300℃×12h, which is 105%, 9% and 17% higher than that of the blank sample, the sample with the optimal amount of Fe2O3 and the sample with the optimal amount of biomass graphene microflakes, respectively. In the study of low permeability modification of silicone rubber sealing material, talcum powder and graphite powder filling modification and fluorine/silicone rubber blending modification are used respectively. The filling modification study showed that both modified talc and modified graphite powder could significantly improve the air tightness of silicone rubber, and the comprehensive performance of the sample with modified graphite powder was better than that with modified talc powder. The optimal filling amount of the modified graphite powder is 15phr, and the gas permeability parameter of the sample is 5.16×10-15mol·m/ (m2·s·Pa), which is 26% lower than that of the blank sample. The study of fluorine/silicone rubber blends shows that the reduction effect of fluorine/silicone rubber blends on the permeability of vulcanized rubber is significantly better than that of modified talcum powder and modified graphite powder. When the total amount of fixed raw rubber is 100phr and the fluorine rubber blend ratio is 30%, the comprehensive performance of the blend is the best. The 200% fixed elongation stress of the sample is 38% higher than that of the sample without blending, and the oil resistance volume change and gas permeability parameters are 12% and 45% lower, respectively.