Carbon blacks, synthetic silicas, quartz, and metal oxides which have large surface areas ranging from 30 to 400 m2/g are very effective in improving mechanical properties of rubber.14 Carbon blacks and silicas are the most widely used fillers in rubber reinforcement and in recent years silicas have been replacing carbon blacks in many industrial rubber compounds. However, silicas are acidic15 and polar16 because of the presence of silanol or hydroxyl groups on their surfaces. This causes unacceptably long cure times and slow cure rates,17 and also loss of CLD in sulfur-cured rubbers.18 To remedy the problems aforementioned, bifunctional organosilanes also known as coupling agents, for example bis(3triethoxy silylpropyl)-tetrasulfide (TESPT), are added to modify silica. The addition of an increasing loading of TESPT improved dispersion of silica particles in rubber.19 Silica and TESPT interact in two ways. Firstly, silica and TESPT are mixed together in the required ratio and homogenized in an additional preliminary mixing stage.20 Alternatively, silanization is carried out in situ. This is usually done in an internal mixer at the first stage of mixing, where TESPT is added together with or after the addition and dispersion of the silica.21