Energy dissipation accompanying Mullins effect of nitrile butadiene rubber/carbon black nanocomposites

Mullins effect of carbon black filled nitrile butadiene rubber compounds and vulcanizates during cyclic tensile deformation is investigated and the influences of thermal annealing of the stretched samples, the deformation velocity and history and the solvent swelling are discussed. The energy losses associated with recovery hysteresis and softening accompanying the Mullins effect at a given crosshead velocity are quantitatively analyzed. The results show that the recovery hysteresis involves in microscopic deformation of the rubber phase in the nanocomposites but it disappears in the swollen samples. On the other hand, the softening is associated with both the rubber and filler phases; its energy loss increases with increasing filler content and decreases significantly by swelling. Furthermore, the softening of samples stretched at room temperatures is recoverable after conditioning at 80 °C but the recovery is retarded significantly by filler. The investigation allows gaining recognition of the important role played by the viscoelastic rubber matrix and the influence of the filler.