Effect of nano CaCO3 on thermal properties of styrene butadiene rubber (SBR)

Styrene butadiene rubber (SBR) as matrix was reinforced separately with 9, 15 and 21 nm sizes of CaCO3, which were synthesized by matrix mediated growth technique. The mixing and compounding was done on two-roll mill and sheets were prepared in compression molding machine. The effect of nature and loading of nano CaCO3 on these rubber nanocomposites was investigated thoroughly by different characterizations such as DSC, TGA, XRD, and mechanical properties. An appreciable increase in glass transition temperature has been observed from DSC study. 9 nm sizes of CaCO3/SBR composites show more increment in Tg as compared to pristine SBR as well as different sizes of CaCO3 filled SBR. This increment in Tg is due to restricted mobility of nano CaCO3 filled SBR nanocomposites. XRD study of nanocomposites showed that nano CaCO3 dispersed uniformly throughout the matrix because of the small peak at lower 2 theta. This uniform dispersion of nano CaCO3 contributes towards the higher mechanical properties of rubber composites. From TGA study, it was observed that as the size of CaCO3 reduces the thermal stability increases as compared to pristine SBR. The other results of these rubber nanocomposites were compared with commercial CaCO3 filled SBR.