Use of Antioxidant-modified Precipitated Silica in Natural Rubber

Fillers play a dominant role in modifying the properties of the base polymer. Precipitated silica is a promising non-black filler for rubber vulcanisates. As silica is hydrophilic and rubber is hydrophobic, uniform dispersion of silica in rubber is difficult and gives rise to problems such as high initial viscosity. Silica has a number of hydroxyl groups, which result in filler–filler particle agglomeration and reagglomeration. Incorporation of silica into rubber is quite difficult compared with the incorporation of carbon black. The main aim of this study was to reduce the hydrophilicity of silica by coating antioxidant onto its surface, and hence achieve easy incorporation of silica into rubber. The preparation of antioxidant-modified precipitated silica and its use as filler in rubber compounds were investigated. The curing and mechanical properties of the compounds were compared with those of conventional compounds containing unmodified silica and antioxidant in the same dosage on natural rubber. The cure and mechanical properties were found to be superior for modified silica composites compared with unmodified silica composites.