The natural rubber with silica masterbatch was produced and used as based material in rubber compound modified from standard tread formulation given in ASTM E 1136. The reduction of mixing energy and rubber vulcanizate properties were investigated. Results indicate that in comparison with STR 5L compound the rubber with silica masterbatch i.e. fresh latex (FNRmSi) low viscosity natural rubber used 1.0 phr of hydrogen peroxide (LNR1mSi) and low viscosity natural rubber used 0.34 phr of hydrogen peroxide and 2.7 phr of potassium persulphate mixture (LNR2mSi) provides maximum mixing energy saving of 30.48% 33.37% and 37.20% respectively. The scorch time and cure time rise with increasing filler loading. The mechanical properties of LNR1mSi and LNR2mSi are similar to those STR5L compound whereas FNRmSi vulcanizate shows superior mechanical properties such as 300% modulus tear resistance abrasion resistance elongation at break and tensile strength. The homogenous distribution and interfacial interaction of silica filler and natural rubber matrix were enhanced by the self-assembled silica masterbatch as shown by the fracture surfaces morphology of the vulcanizate using a Scanning Electron Microscope (SEM). The silica masterbatch form has reduced the mixing power consumption and enhanced the mechanical properties.

The reduction of calcium carbonate (CaCO3) particle was prepared by wet grinding method with 40% dispersion. The particle sizes of CaCO3 were studied with various time of wet grinding. It was found that the particle sizes of CaCO3 rapidly decreased in 3 day of grinding after that it was slightly reduce. Therefore the CaCO3 at various time of wet grinding were mixed with concentrate latex (60% dry rubber content DRC). The result showed that the wet grinding for 2 days provided the superior machanical properties. In addition the compound with epoxidized natural rubber (ENR) as a coupling agent was investigated. It was found that the 5 phr of 30% mole percent of ENR results in significantly improved mechanical properties of the rubber vulcanizates.