Structure and properties of styrene-butadiene rubber/pristine clay nanocomposites prepared by latex compounding method

Styrene-butadiene rubber (SBR)/clay nanocomposites were prepared by mixing the SBR latex with aqueous clay dispersion and co-coagulating the mixture. Tapping mode AFM and XRD were applied to characterize the structure of nanocomposites. It was found that fully exfoliated structure could be obtained by this method only when the low loading of layered silicate (< 10 phr) is used. With increasing the clay content, both non-exfoliated ( stacked layers) and exfoliated structures can be observed simultaneously in the nanocomposites. The results of mechanical tests on the vulcanized pure SBR and SBR/clay nanocomposites showed that the nanocomposites presents better mechanical properties than clay-free SBR vulcanizate. Furthermore, initial modulus, tensile strength, tensile strain at break, hardness ( shore A) and tear strength increased with increasing the clay content, indicating the nanoreinforcement effect of clay on the mechanical properties of SBR/clay nanocomposites. Compared to the clay free SBR vulcanizate, the nanocomposite vulcanizates exhibit a lower tan delta peak value, higher storage modulus and higher tan delta value at the rubbery region (0-60 degrees C) which indicate that the elastic responses of pure SBR towards deformation are strongly influenced by the presence of nanodisperced natural sodium montmorillonite layers especially completely exfoliated silicate layers.