A study on stress-softening of nitrile butadiene rubber reinforced by in situ zinc dimethacrylate

The stress-softening behavior of nitrile butadiene rubber reinforced by in situ zinc dimethacrylate was studied. The degree of stress-softening effect in the fourth stretch-strain cycle of the nitrile butadiene rubber with 10 phr zinc dimethacrylate was only 1.03 (strain = 100%), while it reached to 50.39 at 40 phr zinc dimethacrylate (strain = 200%). The stress-softening effects of carbon black and silica filled nitrile butadiene rubber were also studied, which was used to compare the different stress-softening mechanisms of zinc dimethacrylate. Mooney-Rivlin semi-empirical equation was introduced here to analyze the stress-strain behavior of the nitrile butadiene rubber/zinc dimethacrylate, and the results showed that the nitrile butadiene rubber/zinc dimethacrylate system has an apparent Payne effect and it is easy to achieve the inextensibility limit of rubber chains. Crosslink density analysis indicated a high ionic crosslink density in the nitrile butadiene rubber filled with high content zinc dimethacrylate, which contributed to the low elastic-recovery of the stress-softening.