Effect of chemical structure on the wear behaviour of polyurethane-urea elastomers

The wear behaviour of a series of polyurethane-urea elastomers of two hardness levels, 83/90 Shore A, made with two different curatives and a range of stoichiometries was studied using two different methods. In a high-speed slurry erosion test, wear was higher in the harder polymers but in a Dry Sand Rubber Wheel test, the softer polymers underwent greater wear. This change in rankings of the polymers was associated with a change in the wear mechanism from cutting and gouging in the slurry test to a fatigue mechanism in the Dry Sand Rubber Wheel test. In both wear tests and for the two levels of hardness tested, polymers cured with MBOCA were more wear-resistant than those cured with ETHACURE which was linked to a higher level of crosslinking in the MBOCA polymers. Decreasing the stoichiometry of the softer 83 Shore A ETHACURE polymers introduced crosslinks into these polymers and there was a corresponding increase in the wear resistance. High surface temperatures occurred in the high speed slurry tests, and these probably resulted from hysteresis in the polymers. Softening of the polymers may also have contributed to the variation in performance of the different polymers