Morphology and viscoelastic behaviour of a silica filled styrene/butadiene random copolymer

An investigation into styrene-butadiene rubber and styrene-butadiene rubber/butadiene rubber composites was conducted, aimed at investigating the influence of surface modification of silica on polymer-filler interactions. Two silanes, bis-triethoxysilylpropyltetrasulfane and octadecyltriethoxysilane, were used as surface modifiers. A morphological investigation by transmission electron microscopy and automated image analysis provided a quantitative evaluation of the filler distribution in the rubber matrix by using morphometric descriptors, such as projected area, perimeter and area/perimeter ratio. The better dispersion of the surface-modified silica nicely relates with the improved dynamic-mechanical and tensile properties and accounts for the higher critical concentration necessary to the formation of the secondary network, thus confirming that the surface modification reduces filler-filler and enhances polymer-filler interactions.