Effect of Filler Loading on the Mechanical Properties of Epoxidized Natural Rubber (ENR 25) Compared with Natural Rubber (SMR L)

Abstract

The mechanical properties viz., tensile strength, elongation at break, tear strength and fatigue life of epoxidized natural rubber (ENR 25) was studied using a semi-efficient vulcanization system. Carbon black and calcium carbonate were chosen as the fillers with loading up to 60 phr. SMR L grade natural rubber was used for comparison purposes. Tensile property, tear strength and fatigue life were determined by using a Monsanto Tensometer T10, Instron Universal Tensile Tester and Fatigue To Failure Tester respectively. Results indicate that the tensile property increases with filler loading up to a maximum value after which it drops with further loading of filler. This observation is attributed to the dilution effect of filler after the maximum level of reinforcement. However, the fatigue life decreases steadily with increasing filler content, a finding which is associated with the chain immobility with increasing filler concentration. Carbon black and calcium carbonate show varying effects on the properties investigated whereas SMR L exhibits better tensile properties but poorer fatigue life than ENR 25. Scanning electron microscopy was used to support the observed trends in mechanical properties.