Tear fatigue behavior of lignin-based sustainable rubber composites

Rubber products, especially tire, experiences millions of fatigue cycles during their service life. In this period, penetration or cuts owing to any sharp objects brings calamitous failure. Thus, the fatigue crack growth (FCG) characteristic of tire components has become an important parameter to inspect. In the present study, the FCG behavior of sustainable filler, lignin-filled composite is investigated. The impact of rubber matrix (epoxidation of natural rubber) on crack growth behavior is scrutinized in this article. Epoxy group introduction in natural rubber leads to a significant change in tearing energy throughout the strain range (10%-25%). Higher mol% of the epoxy group brings in a lower crack growth rate. An increase in polar interaction amongst the matrix through epoxide-hydroxyl functionality contributes significantly to the FCG rate. Inter-molecular interaction promotes higher cross-link density in epoxidized natural rubber containing composites which are reflected in static as well as dynamic-mechanical properties. Morphological evidence (Field-emission scanning electron microscope [FE-SEM] and microscopic images) establishes the fact that stiffening at the crack tip, arising from intrinsic strain-induced crystallization and high-density network formation in the concerned matrix are the major contributors to the reduction in fatigue crack growth rate of a composite.