Cast polyurethane elastomers with improved dynamic fatigue resistance

Abstract

AbstractCast polyurethane (PU) elastomers have been widely used in dynamic applications, such as rollers and wheels, where a low heat buildup, high‐loading resistance, and good cut‐growth resistance are desired. Because of their different molecular structure, cast PU elastomers do not perform in the same way in highly demanding dynamic applications. Small variations in the viscoelastic properties can result in significant differences in the longevity of the wheels and rollers that are subjected to a large number of cyclic compressive deformations. Therefore, it is of great interest to understand dynamic performance of urethane elastomers based on various backbones. Dynamic mechanical analysis (DMA) is commonly used to differentiate the dynamic performance of elastomers, but it only provides characterization of the dynamic behavior of a given elastomer at small deformation in the linear viscoelastic regime, where information such as the heat buildup and load‐bearing capability of elastomers cannot be obtained. As such, we developed a stress‐controlled flexometer on the basis of the ISO4666/4 method that enabled measurement of the heat buildup and load‐bearing capabilities of urethane elastomers in a large dynamic deformation environment. Moreover, a dynamometer was constructed to evaluate wheels based on different urethane elastomers under load at various speeds; this allowed close simulation of the urethane elastomers in a real application environment. In this article, the viscoelastic properties of cast urethane elastomers based on different backbones were studied by DMA. The heat buildup and load‐bearing capabilities of the elastomers were investigated via the stress‐controlled flexometer, and the performance of the wheels based on various prepolymer systems were evaluated with the dynamometer. Correlations between the material viscoelastic behavior and the heat buildup were established. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012