]The elastic nature of polyurethanes makes them ideal candidates for applications where continuous flexing is experienced. However, when an elastomer is flexed continuously, failure generally occurs due to the development and propagation of cracks. The cracks form due to localized areas of high stress, where the elastomer is strained. If a crack develops it will continuously grow because the mechanical properties of the part are diminished, leading to ever-increasing stresses and strains.

Fortunately, there are several design considerations that can be taken into account to ensure long service lives for polyurethane parts. Due to the high strength and load-bearing ability of polyurethane, it can be used in thinner sections than other elastomers. By using thinner sections, stresses and strains are kept at a reasonable level when the elastomer is flexed.

Here at the Gallagher Corporation, the Texus Flex method is most commonly used. With Texus Flex, several samples can be tested at the same time at a desired temperature to get a full understanding of how different materials will stand up in specific environments. It should also be noted that laboratory testing for flex fatigue is useful for laboratory comparisons but the correlation between test results and service performance is quite difficult.

Furthermore, flex fatigue can be adjusted by adjusting the chemistry of the polyurethane elastomer. Flex fatigue testing can be useful in trying to determine the expected service life of a polyurethane part. Please contact us for more information and find out how we can put our polyurethane expertise and testing capabilities to work for you.

There are several accepted laboratory tests for comparing the flex fatigue of polyurethane elastomers. Image below shows the general layout of these tests. Click image to enlarge.

Polyurethane Testing Options