Tensile and Tear Behavior of Anisotropic Double Networks of a Black-Filled Natural Rubber Vulcanizate

Abstract

Abstract Double networks of a black-filled natural rubber composition have been prepared by partially curing a sheet, stretching it, and then completing cure. Upon release, a double network retracts to a residual extension ratio, αr. Samples cut perpendicular to the stretch direction have stress—strain responses like the isotropic single network, while parallel samples have enhanced stiffness and tensile strength, and reduced extensibility. Tensile strength is rather weakly dependent on αr. Tear strengths of the double networks, determined using edge-cut strip specimens, exceed that of the single network for low αr. However, when αr is high, double networks have very low tear strengths. Consistent with previous studies, high tear strengths are associated with extensive longitudinal cracking.