Insight on Atmospheric Hydrothermal Aging for Polyester and Polyimide Film Used in Dry-Type Reactor

The breakdown of the dry-type reactor induced by being exposed to moisture needs to be further explored. For this purpose, as the common insulating films in the dry-type reactor, PET and PI films were targeted to investigate the effects of atmospheric hydrothermal aging on the microstructure, thermal stability, and mechanical properties of the films. As the result of hydrothermal aging, the moisture-based thermal degradation obviously occurred on the surface of both PET and PI films, even at a low temperature. More defects and flaws can be observed on the surface of PET than that of PI film, which were responsible for decreasing the transmittance and tensile strength of films. According to the statistical analysis with a one-sample t test, the thermal stability of aged PET and PI films has no significant difference with raw films during the hydrothermal aging. Compared with thermal stress, the hydrolysis of ester linkage and the imide ring are the main factors of hydrothermal aging for PET and PI films, respectively. Improving the waterproof ability of PET and PI films can be effective to prevent deterioration of the interturn insulation performance of the dry-type reactor