Prepartion Of High Stength And Heat Resistant Silicone Rubber And Study On Their Properties

Silicone rubber（SR）is widely used in various fields due to its excellent thermal resistance,electrical insulation and solvent resistance,etc.However,compared with general purpose diene rubber,the lower tensile strength of SR limits its application.Although SR has good heat resistance,how to improve its thermal resistance grade is still the main research direction of high-performance SR to meet the requirement of cutting-edge fields.In order to improve the tensile strength and thermal resistance of SR,this thesis studied the effects of maleamic acid（MAA）,phenyl vinyl silicone rubber（PVSR）,cerium（Ce）-ferric（Fe）complex oxide and novel crosslinking agent used for condensation type liquid silicone rubber on the mechanical properties and thermal resistance of SR.The main research works are as follows:Maleamic acid（MAA）,hexamethyldisilazane（HMDS）and vinyltriethoxysilane（VTEO）were used to modify SR/silica composites,respectively and the modification effects of the three modifiers on the composites were compared.The results show that MAA can effectively promote the dispersion of silica in SR.In addition,the tensile strength of maleamic acid modified composites were higher than those of SR/silica/HMDS and SR/silica/VTEO composites.Besides,the lowest compression relaxation rate and compression set were also achieved by SR/silica/MAA composites.A series of Ce-Fe complex oxides with various Ce/Fe molar ratios were prepared via a citric acid sol-gel method,which were added into SR as thermal oxidative stabilizers.The effect of Ce/Fe molar ratio in complex oxide on the thermal oxidative stability of SR was studied.After aging at300°C for 24 hours,SR filled with Ce-Fe complex oxide（Ce/（Ce+Fe）molar ratio is 0.8）has highest tensile strength and elongation at break retentions among all the prepared composites.Vinyl silicone rubber（VSR）/PVSR blends with various different blend ratios were prepared.The mechanical properties of blends were on downtrends with the increasing addition of PVSR because of the imcompatabilty of the two phases,while the thermal resistance and damping properties were significantly improved.The VSR/PVSR blend with a blend ratio of 80:20 has the best thermal oxidative stability among all blends.Besides,the introduction of PVSR increased the damping temperature range and also resulted in the shift of glass transition temperature to a higher value.Inspired by the dissipated energy mechanism of the sacrificial bond and the molecular design of the thermal resistant silane coupling agent（SCA）,this work synthesized a novel thermal resistant SCA named ATA-SCA through the reaction between 3-amino-1,2,4-triazole（ATA）and 3-Glycidoxypropyltrimethoxysilane（KH560）.ATA-SCA was then used as the crosslink agent of liquid silicone rubber（LSR）.With the addition of ferric trifluoromethanesulfonate,the Fe³⁺-triazole metal coordination bonds were introduced into the crosslink network of condensation type LSR.In comparison with LSR crosslinked by KH560,ATA-SCA crosslinked LSR has higher tensile strength and elongation at break,and also significantly higher tensile strength and elongation at break retentions after aging at250°C for 3 days.