Tailoring reinforcement and strain softening behaviors of natural rubber vulcanizates nanocomposites by dopamine-modified silica

Filler is extensively used to reinforce rubber vulcanizates but it invariably enhances softening under largeamplitude oscillation shear and large-strain cyclic tension, yielding an awkward paradox between improving the elasticity and reducing the softening. Herein dopamine modified silica is used to fill natural rubber (NR) vulcanizate for tailoring elasticity, strength and softening behaviors. The results show that, in comparison with hydrophilic silica in combination with silane, the modified silica prepared with the freeze drying method is able to improve crosslinking density of NR, dispersity of filler, and tensile strength and extensibility of the nanocomposites and at the same time weaken the dissipation and softening accompanying with Mullins effect of the nanocomposites. The softening of nanocomposites is accounted for and the contribution of filler is revealed within the framework of strain-concentration superposition principle taking into consideration of crosslinking density of NR and strain amplification factor induced by the filler. The investigation is enlightening for tailoring elasticity and dissipation for vulcanizate nanocomposites and for paving the way to manufacture highperformance rubber nanocomposites with reduced mission of volatile organic compounds.