UV degradation of poly(ether imide) film under vacuum condition and its examination by chemical analyses

Polymers are widely used in space as thermally controlled materials. Among them, polyetherimide (PEI) stands out and is a promising candidate as a thermally controllable material because of its high durability and transparency. However, the degradation mechanism under ultraviolet (UV) light in the space environment is not completely known. In this study, we monitored the degradation of PEI under UV light irradiation in a vacuum atmosphere to simulate the space environment. Chemical analyses were performed using X-ray photoelectron spectroscopy (XPS), surface attenuated total reflectance infrared (ATR-IR) measurement, and cross-sectional ATR-IR measurement. The relationship between the solar absorptance with increasing irradiation dose and chemical degradation was also a subject of study. XPS measurements revealed that structural changes occurred within a few nanometers of the surface in a relatively short time after irradiation. Additionally, there was nearly no change even when the irradiation dose was increased thereafter. Surface ATR-IR measurements demonstrated that a region of several micrometers on the surface gradually underwent structural changes owing to the formation of a crosslinked structure upon UV irradiation, and cross-sectional ATR-IR measurements indicated that were more closely correlated with the value of solar absorptance. • Polyetherimide (PEI) is a promising thermally controllable material for space use. • UV-induced degradation of PEI in a vacuum was monitored to simulate the space environment. • XPS analysis revealed rapid structural changes within a few nanometers of the surface. • Surface ATR-IR showed gradual crosslinking-induced structural changes in micrometer regions. • Cross-sectional ATR-IR analysis correlated degradation depth with increasing solar absorptance.