Preparation of SiO2 particles with silicone-methoxy groups on surface and its co-curing hydroxyl silicone oil

SiO2 particles were modified by γ-aminopropyltriethoxy silane (KH550) and γ-(2,3-epoxypropoxy)propyltrimethoxy silane (KH560) in sequence to prepare SiO2 particles with silicone-methoxy groups on surface (SiO2-s-Si(OCH3)3). X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) were used to characterize the modified SiO2 particles. The SiO2-s-Si(OCH3)3 particles and tetramethoxysilane were used to co-cure hydroxyl silicone oil. The strong interfacial interactions between silicone rubber and fillers, which came from hydrolyzed SiO2-s-Si(OCH3)3 particles in situ reacting with hydroxyl silicone oil, had a great effect on the properties of composites. The mechanical properties, thermal conductivity, dielectric strength and volume resistivity of SiO2-s-Si(OCH3)3/silicone rubber composites were considerably higher than that of pristine SiO2/silicone rubber composites at the same content of SiO2, while the dielectric constant and dielectric loss tangent of SiO2-s-Si(OCH3)3/silicone rubber composites was lower than that of pristine SiO2/silicone rubber composites at the same content of SiO2.