Scanning electron microscopy study on the influence of temperature on tear strength and failure mechanism of natural rubber vulcanizates

All these parameters exert profound influence on the failure pattern, as obtained in the SEM photographs of the vulcanizates subjected to tear fracture. The peroxide cured vulcanizate gives rise to stick-slip type of tear with striations and microfolds on the surface, while sulphur curing of the vulcanizate generates a failure pattern which indicates an origin of multiple fracture paths and their subsequent conversion into shear planes at a higher crosslink density. In the case of carbon black filled samples, a coarse fracture surface with convergence of tear paths and formation of many short rounded tear lines are observed. The vulcanizates show maximum tear resistance at the level of achieving optimum crosslink density. However, the strength drops sharply at elevated temperatures.