Effect of reinforcement type and viscoelasticity on static crack growth, fatigue, and creep resistance in acrylonitrile butadiene rubber (NBR) elastomers

Various mechanisms contribute to the failure of engineering rubber products, including static crack growth, dynamic crack growth (fatigue), thermal accumulation, and creep failure. The viscoelasticity, which is greatly affected by the particulate or resin-based reinforcement, plays a controlling role in most of these failure phenomena. Here, the failure mechanism of the NBR (Nitrile-butadiene rubber) matrix filled with particulate carbon black (CB N660) or a high styrene resin (HSR) is investigated by performing various experimental tests. In addition, finite element analysis was adapted to calculate the J-integral as a crack propagation driving force numerically. Adding 30 phr HSR to a carbon black-filled rubber uniquely modified each failure mechanism. It increases the linear and non-linear viscoelastic loss, leading to a 3-fold increase in static crack growth resistance and a 46% increase in fatigue crack growth resistance. However, the creep resistance experienced a 100% reduction, and the propensity for the crack growth unfavorably underwent a 5-fold increase. The fracture pattern of samples with a high percentage of HSR was knotty. The resistance against creep and fatigue crack growth was remarkably reduced, where part of the particulate filler was substituted with the HSR resin.