Analysis of the Degradation Kinetics of Kapton Film in an Aerospace Environment

Abstract

This paper describes the results derived from thermogravimetric analysis (TGA) work on poly (4,4‘-oxydiphenylene-pyromellitimide), or more commonly known as Kapton film. The test are completed under heating rates of 5, 10, 20, and 50 K/min and two distinct atmospheres, concentrations of 21 % and 3 % oxygen. The atmospheres chosen mimic the oxygen concentrations at ground-level and at a cruising altitude of 15 km, which are the two extremes of the environments the insulation is expected to operate in when being applied in commercial aircraft electrical systems. From the rate of TGA conversion data at various temperatures, kinetic parameters such as the activation energy (Ea) and pre-exponential factor (A) are found. This is then used to illustrate the relationship that can exist between oxygen concentrations and the ageing and degradation rates of polyimide insulation as expressed using the Arrhenius equation. From this, differences between the ageing mechanisms and relative lifetimes of insulation systems in an aerospace application compared to those operating in ground-based systems can be found.