Investigating the impact of manufacturing conditions on crack growth rate in nitrile butadiene rubber for enhanced service life – Part 01

Extended service life of components is playing an increasingly important role in society and economy. Accordingly, this also applies to elastomeric materials, which are used for example for tires, seals, and hoses. These are often exposed to cyclic loading, with crack initiation and growth playing a decisive role. Corresponding phenomena have been investigated for many years and are still not fully understood. For the fatigue behavior, the crosslinking state of the material is of particular importance. This is accompanied by various production parameters, such as processing temperature and curing time, which have been of little importance in research to date. For this reason, plain strain test specimens out of nitrile butadiene rubber (NBR) were produced by injection molding at different mold temperatures and crosslinking times in the present work. With the aid of these, the crack growth rate at different crosslinking states under cyclic loading was investigated. It has been shown that a longer crosslinking time toward fully cured specimens results in a 20% reduction in dissipated energy, with a corresponding increase of the crack growth rate by the factor of 100. Furthermore, a 20 K increase in mold temperature during manufacturing of fully cured specimens leads to a four times slower crack growth.