Degradation Study of Aromatic and Aliphatic TPU Films in Accelerated Weathering: Impact on the Gas Barrier and Mechanical Properties

This study investigates the influence of the artificially accelerated weathering test on the degradation behaviour of thermoplastic polyurethane (TPU) films. Accelerated artificial weathering test parameters were specially designed to simulate outdoor natural exposure parameters with higher UV radiation exposure. Artificial weathering tests were carried out in a laboratory weatherometer and changes in mechanical properties, chemical structure and morphology were studied. In this study, two types of polyether-based aromatic and aliphatic TPU films were exposed for 500 h. The result shows that exposure to UV radiation affects the key properties like breaking strength, helium gas barrier and surface properties of TPU films. The mechanical strength reduces as the irradiance time is increased. The SEM and AFM analysis reveal that the film surface that was exposed to irradiance become rough, and cracks on the surface were observed. The FTIR analyses of the exposed film prove that chemical structure changes due to the formation of the polyurea group. It was found that aromatic TPU gets crosslinked after 300 h exposure; however, in aliphatic TPU, long molecular chains break into shorter chains, and the number of chain scission increases with increasing exposure time.