Hydrophobic nano silica sols with different specific surface area were prepared and incorporated into vinylmethylpolysiloxane (VMQ). and effects of the specific surface area and content of hydrophobic nano silica on the mechanical properties of high temperature vulcanized (HTV) silicone rubber were investigated. HTV silicone rubbers filled with three types of fumed nano silica were also prepared for comparison with HTV silicone rubber reinforced by hydrophobic nano silica sol. The mechanical properties datashowed that when used in VMQ, hydrophobic nano silica sol exhibited even stronger reinforcing ability than fumed nano silica. In fact, the reinforcement of only 30 phr(per hundred rubber) hydrophobic nano silica sol greatly exceeded that of 40 phr(per hundred rubber) fumed nano silica. Based on the different specific surface area, interfacial property and observations via transmission electronic microscope (TEM), possible mechanism for the different reinforcement of two kinds of filler were analyzed and discussed preliminarily.
