Competition between Strain-Induced Crystallization and Cavitation at the Crack Tip of Unfilled and Carbon Black-Filled Natural Rubber

Structural changes at the crack tip of unfilled and carbon black-filled natural rubber under static deformation were investigated using synchrotron-based small- and wide-angle X-ray scattering. The distributions of cavities and crystallites at the crack tip were determined at different external strain levels. It was found that the addition of carbon black not only enhances strain-induced crystallization but also prevents the formation of cavities. The competition between the enhancement of strain-induced crystallization and the damage caused by cavitation is discussed. An explanation for the occurrence of sideways cracks in filled natural rubber from the microscopic point of view is suggested.