Adjusting the properties of silicone rubber filled with nanosilica by changing the surface organic groups of nanosilica

A series of nanosilica (denoted as nano-SiO2) surface-capped with organic modifiers hexamethyldisilazane (denoted as HMDS; molecular formula: C6H19NSi2) and KH570 (molecular formula: C10H20O5Si) containing CC double bond were prepared by in situ surface-modification method. As-obtained nano-SiO2 particles were characterized by Fourier transform infrared spectrometry and transmission electron microscopy, and they were also used to reinforce silicone rubber (denoted as SR) in order to improve the mechanical properties. Moreover, a universal material testing machine was performed to determine the mechanical properties of the SR-matrix nanocomposites. Results showed that the surface properties of nano-SiO2 can be adjusted by changing the ratio of these modifiers. The tensile strength, tear strength and elongation at break of nano-SiO2/SR nanocomposites are comparable to or even better than those of R-106/SR nanocomposite (R-106 refers to commercially obtained fumed SiO2 nanoparticles that was modified with silane coupling agent). The mechanical strength of nano-SiO2/SR nanocomposites especially for tear strength largely improve with adding a small amount of CC content of the surface-capped nano-SiO2. More importantly, it could be feasible to manipulate the mechanical properties of silicone rubber by properly adjusting the dosages of surface-modifiers HMDS and KH570 during the preparation of in situ surface-capped nanosilica, which could be of special significance to developing high performance SR-matrix nanocomposites.