The silica treated with methanol, dichloromethylsilane or dimethyldichlorosilane was used as the filler for rubbers and the effect of these fillers on the mechanical properties of rubbers was examined. With the measurement of hardness and stress-strain behaviour for the vulcanized samples the effects of contents and kinds of fillers on the mechanical properties of SBR or NR were studied.
The hardness was increased with the contents of fillers and treated silica showed the pronounced effect for SBR but no significant change for NR. Tensile strength at 300 % elongation showed the similar tendency but the critical content of 30 phr appeared for NR. Tensile strength and elongation at failure were increased with the content of filler up to the critical content. For the above amount of critical content of filler, the tensile strength and elongation at failure showed no change for SBR but decreased for NR.
With IR spectra of the unvulcanized rubber specimen filled with silica, it was found that the interaction site of fillers and rubber molecules was different for various silica.