Preparation And Properties Of Aryl Silicon Rubber Ablative And Heat Shield Materials

Silicon carbide matrix composites have been considered as one of those promising materials aaplied in various hermal protection system?TPS?for space vehiclesdue to their high strength,sound stiffness,low density,light weight and high temperature sustainability.For example,silicon rebber composites are used to prouduce rocket combustion chambers and to provide insulation to Solid Rocket Motors.However,a major problem is that integrated chars among different layers can be yielded during ablation test,and these brittle chars were prone to peel off the underlying material.Prepolymers of polyarylacetylene?PAA?have a lot of advances such as high char yield and excellent heat absorption ability during pyrolysis.In this paper,the modification of silicone rubber by polyarylacetylene in order to increase the ablation resistance of silicone rubber,and strengthen its high temperature environment service capacity.Firstly,aryl silicon rubber ablation resistant and heat shield material was prepared using methyl vinyl silicon rubber?VMQ?and methyl phenyl vinyl silicone rubber?PVMQ?as matrix,white carbon black as reinforced fillers,and add prepolymers of polyarylacetylene.The study of the effect of PAA content on the properties of silicone rubber was used to determine the basic formula of the aryl silicon rubber ablation resistant and heat shield material.Experimental results show that the char yield?at 800 ??of PAA was 83.75 %.The char yield of the aryl silicon rubber ablation resistant and heat shield composite material with 10 PAA is 167.08 % more than silicon rubber samples.And the linear rate was 0.135 mm/s,the tensile strength was 4.37 MPa.The overall performance of the aryl silicon rubber ablation resistant and heat shield composite material with 10 PAA was the best.Carbon fibers?CF?filled silicon rubber ablation resistant and heat shield material was prepared using carbon fibers as fills under the basic formula of the aryl silicon rubber ablation resistant and heat shield material,and the effect of carbon fiber content on the properties of the aryl silicon rubber ablation resistant and heat shield material was investigated.Experimental results show that all the aryl silicon rubber ablation resistant and heat shield materials with CFs exhibited worse mechanical properties and ductility.The tensile strength and elongation at break of samples filled 50 CF were 3.25 MPa and 77% respectively.And the linear ablation rate was 0.050 mm/s,the ablation layer structure is compact,and the ablation layers can resist the erosion of high temperature and high speed air flow.These ablation layers were harder to peel off the underlying material.ZrO₂ filled aryl silicon rubber ablation resistant and heat shield material was prepared using ZrO₂ as ablation resistant fills under the basic formula,and the effect of ZrO₂ content on the properties of the aryl silicon rubber ablation resistant and heat shield material was investigated.Experimental results show that the low linear rate of samples filled with 50 phr ZrO₂,owing to the serious splash during in the ablation process.The incorporation of 40 phr ZrO₂ improved the tensile strength and linear ablation rate of the ZrO₂ filled silicon rubber ablation resistant and heat shield material by 4.47 MPa and 0.070 mm/s.The samples filled with ZrO₂ exhibited worse wear resistance properties,because the interaction between ZrO₂ and aryl silicone rubber was very weak,and the ZrO₂ did not dispersed in matrixevenly.Carbon fiber cloths reinforced silicon rubber ablation resistant and heat shield material was prepared use carbon fiber cloths compound with aryl silicon rubber material.The effect of the carbon fiber cloths on tensile strength,ablative performance of aryl silicon rubber ablation resistant and heat shield material.Experimental results show that use the silicone rubber impregnated into the gap of carbon fiber cloths,and the tensile strength of aryl silicone rubber material was improved,because deal with carbon fiber cloths by gas phase oxidation can strengthen the interaction between carbon fiber cloths and aryl silicone rubber.When the content of PAA is 20 phr,thet ensile strength of aryl silicone rubber material reinforced by carbon fiber cloths was 14.25 MPa,compared with the silicone rubber materials the tensile strength increased by 226 %.When the content of PAA is 50 phr,thet ensile strength of aryl silicone rubber material reinforced by carbon fiber cloths could achieve 24.00 MPa.Carbon fiber cloths reinforced could improve the ablative performance of aryl silicone rubber ablation resistant and heat shield material,and the linear rat was 0.074 mm/s,the oxygen acetylene flame was blocked by the surface layer of carbon fiber cloth on matrix material,and the ablation crater was small,and the ablation layers were harder to peel off the underlying material.