Synthesis Of Multifunctional Silane Coupling Agent And Its Application In Carbon Black And Silica Reinforced Isoprene Rubber Composites

Carbon black and precipitated silica are the most commonly used reinforcing agents in the rubber industry.Carbon black has better reinforcement effects and can endow the reinforced rubber with good abrasion resistance,while precipitated silica can enable rubber matrix to generate low hysteresis heat.Carbon black and precipitated silica co-reinforced rubber combines the advantages of both,which is usually used to manufacture high-performance rubber products.However,such inorganic fillers,especially precipitated silica,have limited compatibility with rubber matrix and are difficult to be homogeneously dispersed during the mixing process,which will affect the performance of the rubber products.Therefore,how to enhance the compatibility between carbon black,precipitated silica and rubber matrix is the key to achieving high-performance rubber composites as well as products.In the rubber industry,silane-coupling agents are usually used to modify the surface of carbon black or precipitated silica.Unfortunately,the commercially available silane-coupling agents cannot achieve simultaneous modification of carbon black,precipitated silica and rubber.Based on this,a multi-functional silane-coupling agent,2-aminoethyl-2-(3-triethoxysilylpropyl)aminoethyl disulfide(ATD),is designed and synthesized in this dissertation,which contains amino,triethoxysilyl,and disulfide bond in its molecular structure.Therefore,ATD can simultaneous modify the surface of both carbon black and precipitated silica,and can participate in the cross-linking reaction of rubber.As such,ATD can be used as the modifier for carbon black and precipitated silica co-reinforced isoprene rubber,which lays the foundation for the development of high-performance rubber products.The research contents of this dissertation are as follows.(1)Multi-functional silane-coupling agent,ATD,is synthesized by substitution reaction with cystamine and 3-chloropropylthriethoxysilane as the starting materials.(2)The ATD-modified isoprene rubber(ATD-IR),ATD-modified isoprene rubber and carbon black mixture(ATD-(IR/CB)),and ATD-modified carbon black(ATD-CB)are prepared by mechanical blending and/or solution blending methods.The amounts of ATD grafted onto isoprene rubber and carbon black are determined to be 4.0 wt%and 3.2 wt%,respectively,for the ATD-IR and ATD-CB samples prepared by solution blending method,while grafting ratio can reach up to 4.7 wt%for ATD-IR prepared by mechanical blending method.These result indicate that ATD can separately react with isoprene rubber and carbon black,i.e.,the disulfide bond in ATD can react with isoprene rubber to generate C-S bond,whereas amino and triethoxysilyl groups in ATD can separately react with carboxyl and hydroxyl groups on the surface of carbon black to form the CO-NH and Si-O-C bonds,as evidenced by FTIR and XPS analyses.In addition,there exists hydrogen-bonding interaction between ATD and carbon black.Owing to these reasons,the bound rubber contents can reach up to 0.744 g/g and0.869 g/g,respectively,for the ATD-(IR/CB)samples prepared by mechanical blending and solution blending,again confirming that the ATD can simultaneously react with isoprene rubber and carbon black.And just for this reason,the vulcanization rate and the cross-linking density increase in ATD-modified,carbon black-reinforced isoprene rubber(ACBIR),meanwhile,the dispersion of carbon black in isoprene rubber matrix is ameliorated.The rebound resilience,compression set,abrasion resistance,creep and dynamic mechanical properties of the ACBIR vulcanizates have been improved.The experimental results imply that the optimum performance is obtained for this vulcanizates with an IR/ATD/CB mass ratio of100/1.5/37.(3)The ATD-modified isoprene rubber and precipitated silica mixture(ATD-(IR/Si O₂))and ATD-modified precipitated silica(ATD-Si O₂)are synthesized by mechanical blending and/or solution blending methods.The amount of ATD grafted onto precipitated silica can reach up to 5.6 wt%,which can be attributed to the condensation reaction that occurs between triethoxysilyl group in ATD and hydroxyl group on the surface of precipitated silica together with the hydrogen-bonding interaction between them.In addition,the bound rubber contents reach up to 0.608 g/g and 0.586 g/g,respectively,for the ATD-(IR/Si O₂)prepared by mechanical blending and solution blending methods,also indicating that ATD can simultaneously react with isoprene rubber and precipitated silica.Just for this reason,the vulcanization rate and the cross-linking density increase in ATD-modified,precipitated silica-reinforced isoprene rubber(ASi IR).Meanwhile,the dispersion of precipitated silica in isoprene rubber matrix is ameliorated.The rebound resilience,compression set,abrasion resistance,and creep and dynamic mechanical properties of ASi IR vulcanizates have been improved.The results indicate that the optimum performance is obtained for this vulcanizates with an IR/ATD/Si O₂mass ratio of 50/2/25.(4)The ATD-modified,carbon black/precipitated silica/isoprene rubber composite(ATD-(IR/CB/Si O₂))and ATD-modified carbon black/precipitated silica mixture(ATD-(CB/Si O₂)are prepared by mechanical blending and/or solution blending.As for the ATD-(CB/Si O₂)sample prepared by solution blending,FTIR and XPS results indicate that the triethoxysilyl group in ATD would prefer to react with the hydroxyl group on the surface of precipitated silica,while amino group in ATD is prone to react with the carboxyl group on the surface of carbon black,which lead to an increase in the amount of ATD grafted onto carbon black/precipitated silica,i.e.,5.0 wt%.Additionally,the bound rubber contents increase to 0.698 g/g and 0.818 g/g,respectively,for the ATD-(IR/CB/Si O₂)prepared by mechanical blending and solution blending methods.The processing and physical properties of ATD-modified,carbon black/precipitated silica co-reinforced isoprene rubber(ACSIR)compounds and vulcanizates by mechanical blending are explored in detail.The results indicate that the optimum overall performance is obtained for this vulcanizates with an ATD/IR/CB/Si O₂mass ratio of 3/100/20/30.(5)The as-prepared ACSIR compounds are used for trial manufacture of rubber-metal shear-compression typed,vibration-damping elastic components(SCRMEC),which are compared with the corresponding SCRMEC manufactured from unmodified rubber((Un CSIR))composite as well as Si69-modified,carbon black/silica co-reinforced isoprene rubber(SCSIR)composite.Compared to Un CSIR composite,the tensile property,rebound resilience,compression set,creep property and fatigue property of the ACSIR composite are significantly improved.Moreover,the tensile strength,compression set and heat ageing resistance of this composite are better than those of SCSIR composite.As a result,the width of hysteresis curve,dynamic to static stiffness ratio,and creep resistance of SCRMEC manufactured from ACSIR composite are significantly better than the corresponding SCRMEC manufactured from SCSIR composite,suggesting that ACSIR composite is more suitable for the manufacture of high-performance damping rubber products.