| Flexible joint has many excellent properties and has been widely used in various solid rocket motors.But the elastic part is the core of flexible joint.At present,the elastic piece is more to use the natural rubber and isoprene rubber,however they are difficult to be used in-45 ℃ or more low temperature range.Silicone rubber has excellent high and low temperature resistance and aging resistance,but its mechanical properties is low and difficult to glue,so developing excellent comprehensive properties of silicone rubber to meet the demand of wide temperature range for flexible joints using has the vital research significance and application value.This project mainly researchs the design of silicone rubber formula and adhesive development to improve the mechanical properties and bonding strength of silicone rubber and achieve the performance index of flexible joint wide temperature range.Firstly,the influence of phenyl content on the properties of silicon rubber has been studied.Measured by differential scanning thermal analysis(DSC),dynamic mechanical test(DMA)and tensile resistance to cold to characterize the low temperature performance,the shear properties of the wide range of temperature,curing characteristics and mechanical properties at room temperature are analysed.The results show that with the increase of the content of phenyl,glass transition temperature(Tg)improves and crystallization temperature(Tc)declines.110-2 at-55℃~+ 60℃ and 120-1 at-71℃~+ 60℃,both maintain a steady shear performance.Secondly,formula design and processing of elastic material of wide temperature silicon rubber are studied.At 71℃~+ 60℃,using 120-1 as the research key and using the single factor analysis method to study the crosslinking agent,reinforcing filler,plasticizer and different processing molding process on the properties of silicone rubber.By universal material testing machine,infrared spectrum(IR),thermal gravity analysis(TGA),crosslinking density and scanning electron microscopy(SEM)to characterize the constructure and performance of the silicone rubber.The results show that120-1 silicone rubber has the best comprehensive mechanical properties at 1.0 part cross-linking agent DCP,40 parts of the modified white carbon black,2 parts of ester plasticizer.With the method of analogy,110-2 formula used at-55℃~+60℃ is to use 1.0 crosslinking agent DCP,35 parts modified silica.Using mixer technology Ⅱ,silicone rubber has futher improve comprehensive mechanical properties.Thirdly,research the bonding of silicone rubber and metal with heat vulcanization.The mixture of coupling agent and silicone rubber,metal surface treatment,reinforcing filler and decelopment of adhesive were studied.Through IR analysis and shear test,the results show that the optimizing adhesive 3,the shear strength of silicone rubber of 110-2 and 120-1 can respectivly reach above 3.0MPa and 2.8MPa.The grinding of metal specimens with more than 80 mesh can achieve the rubber cohesive failure.With the increase of reinforcing filler,the shear strength increases gradually,which was close to 4.0MPa.Finally,the flexible joint test piece has been studied.The related features of furnace of silicone rubber are analyzed.The tensile shear cycle of silicone rubber in the wide temperature range and room temperature compression cycle are studied.The 110-2 flexible joint test pieces air-tight performance and high and low temperature swing performance are analyzed.The results indicate that the shear modulus is less fluctuation in the wide temperature range.With the increase of displacement,the shear cycle loss ratio of 110-2 and 120-1 is increased.the compression cycle loss ratio of 110-2 and 120-1 is slightly increased with increasing pressure.The test piece successfully passed the air tightness assessment.The total torque of the test piece increases with the decrease of temperature,and increases with the increase of pressure.In the wide temperature range,the fluctuation range of high and low pressure is respectively between 0.84~1.33 and 0.93~ 1.17. |
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