A Comprehensive Study on the Degradation Behavior and Mechanism of Expanded Thermoplastic Polyurethane.

Expanded thermoplastic polyurethane (ETPU) is used in a wide range of applications due to its excellent properties, but inevitably, aging deteriorates the material properties and shortens service lifetime. This study conducted aging experiments on ETPU to summarize the deterioration trend and provide reliable data. The ETPU underwent three distinct aging protocols: thermal aging for 28 days in a controlled 80 °C environment; xenon lamp aging under continuous UV irradiation (via xenon lamp) at 80 °C for 28 days; and weathering aging through 671 days of outdoor exposure to real-world weather conditions. After various structural characterization and performance tests on the aged ETPUs, the results showed that thermal aging is not the key factor causing the aging of ETPU; the internal structure of ETPU is damaged and the performance rapidly deteriorates under the combined effect of light, heat, and humidity. The special heterogeneous structure gives the sample different internal aging characteristics, and the bead interface becomes a defective site after aging, affecting the overall mechanical properties of the material. In the natural state, the lifetime of ETPU is about two years. Our work will provide valuable data for the study of the aging properties of ETPU and contribute to the prediction of the lifetime of the material.