Cut Growth in Natural Rubber Vulcanizates

Every solid body contains inevitable flaws of various shapes and sizes. When a solid is subjected to a global stress, the local stresses at the tips of these flaws are magnified and can exceed the mean applied stress, and then fracture begins. Griffith1 proposed and energy balance criterion for the fracture of an elastic solid. He postulated that a crack will grow a distance if the elastic energy released by the growth is greater than the surface free energy of the surfaces thus created. However, this criterion is not applicable to rubber. When a crack grows, irreversible processes occur in the vicinity of the tip, leading to energy dissipation that must be made up from the available elastic energy
The research presented investigated the mechanical properties and reinforcement mechanisms of natural rubber (NR) vulcanizates reinforced with carbon black. For both gum and black-filled natural rubber, reversion was lowest by adding intermediate multifunctional acrylate ester as anit-reversion coagent. Tensile tests of the precut NR were carried out. The vulcanizates structure has been examined by cure rheometry, ATR-FTIR and miscroscopy.
References: 1. A. A. Griffith, VI. The Phenomena of Rupture and Flow in Solids, Phil. Trans. Roy. Soc. Lond., 1920, A221, 163