Effect of ionic liquid on structure and properties of carbon black filled natural rubber vulcanizates

Rubber nanocomposites exhibit marked strain softening upon large-amplitude oscillation shear and large-strain cyclic tension while there are rare ways developed for solving the awkward paradox between improving elasticity and weakening softening. Herein ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate, at a content as low as 0.2 parts per hundred parts of rubber was introduced into carbon black (CB)/natural rubber (NR) nanocomposites for regulating the microstructure and viscoelasticity. The results show that IL could accelerate NR vulcanization, improve proportion of polysulfide crosslinking bonds and promote CB dispersity without marked influence on crosslinking density. It is of significance that IL could weaken Mullins effect by reducing dissipation and softening energies. It is fascinating that at CB volume fraction 0.231, IL could improve tensile strength and extensibility and weaken the Mullins effect simultaneously. The investigation is enlightening for tailoring elasticity and dissipation of vulcanizate nanocomposites by regulating the crosslinking network and CB dispersity.