Preparation Of SiO₂ Particles With Reactive Silicone-methoxy Groups And Its Co-curing Hydroxyl Silicone Oil

With the rapid development of integration and assembly technology in the field of electronics and electricity,the volume of electronic components and circuits is shrinking,which puts forward higher requirements for the performance of interface materials.It is urgent to develop silicone rubber materials with excellent thermal conductivity,insulation and strength.In this paper,the surface of SiO₂ powders was firstly bonded with amino functional groups,and then reacted with epoxy silane coupling agent to prepare SiO₂ powders containing reactive siloxane,which could co-crosslink hydroxyl silicone oil with cross-linking agent.The effects of the amount of silane coupling agent,reaction temperature and reaction time on the surface modification of powders were studied.The results show that the suitable amount of 3-aminopropyl triethoxysilane（KH550）is 2 wt%of the powder quality;the suitable amount ofγ-glycidyl ether oxypropyl trimethoxysilane（KH560）is 4 wt%of the powder quality,the reaction temperature is 85℃,and the reaction time is 45 min.XPS,FTIR and TG analysis results confirm that SiO₂-s-Si（OCH₃）₃ containing reactive silicone-methoxy groups has been successfully prepared.The suitable matrix formulation for preparing silicone rubber was determined by using unmodified SiO₂ powder as filler,polydimethylsiloxane as matrix,tetramethoxysilane as cross linker and dibutyltin bis（acetylacetonate）as catalyst.The mechanical properties of silicone rubber showed that the suitable amount of cross-linker and catalyst was 4 wt%and 0.1 wt%of hydroxyl silicone oil,respectively,and the tensile strength of condensated silicone rubber was 0.6 MPa.The effects of SiO₂-s-Si（OCH₃）₃ powders addition and its co-crosslinking with tetramethoxysilane on the properties of room temperature condensation silicone rubber were studied.With the increase of SiO₂-s-Si（OCH₃）₃ powders content,the hardness,mechanical properties,thermal conductivity and insulation properties of silicone rubber increased.When the amount of SiO₂-s-Si（OCH₃）₃ powders is 60 wt%,the tensile strength of silicone rubber is 0.76 MPa,thermal conductivity is 0.55 W/mK,electrical breakdown strength is 23.4 kV/mm,dielectric constant is 4.16 pF/cm at 1 MHz,and the properties of silicone rubber crosslinked with SiO₂-s-Si（OCH₃）₃ powders are obviously better than that of the corresponding unmodified SiO₂ powders,and the dispersion of the powders is obviously improved.SiO₂-s-Si（OCH₃）₃ powders were partially replaced by Al₂O₃-s-Si（OCH₃）₃ powders.The effect of powder ratio on the properties of silicone rubber was studied.With the increase of the proportion of Al₂O₃-s-Si（OCH₃）₃ powders,the thermal conductivity and mechanical properties of silicone rubber were improved,the volume resistivity and electrical breakdown strength decreased,and the dielectric constant and dielectric loss angle increased.When the ratio of Al₂O₃-s-Si（OCH₃）₃ to SiO₂-s-Si（OCH₃）₃ is changed from 40:60 to 55:45,the thermal conductivity increases from 0.574 W/（m?K）to 0.619W/（m?K）,the tensile strength increases from 0.91 MPa to 1.18 MPa,and the dielectric constant at 1 MHz changes from 4.98 pF/cm to 5.52 pF/cm.