Hydrothermal aging of polyimide film

Abstract The hydrothermal aging of a commercial polyimide film, (poly[pyromellitic dianhydride‐co‐4,4′‐oxydianiline]) is investigated, providing further insight into the well‐known loss of properties that can occur for these materials in the presence of moisture. The study involved measuring ATR‐FTIR, ultimate tensile strength, and percent elongation at break, under accelerated hydrothermal aging conditions at three different temperatures (70, 80, and 90°C). ATR‐FTIR data was analyzed using chemometrics in order to identify significant trends that develop upon the accelerated aging conditions. The most dramatic changes were observed for the aging at 90°C. Changes in the ATR‐FTIR spectra for aging at all three temperatures can be attributed to hydrolysis of the imide groups. Ultimate tensile strength was also used to monitor the hydrothermal aging process. This data was used to construct an Arrhenius plot from which an activation energy of 71.8 KJ/mol was determined for the hydrothermal aging process. This value is comparable to that of textiles used in fire protective clothing, suggesting that polyimide is a viable candidate for modeling the degradation of these textiles. This paper also shows the large potential of chemometrics for polymer aging studies as it allows identifying degradation mechanisms from subtle chemical changes in the materials.