Thermo-oxidative degradation of siloxane-containing polyimide and unmodified polyimide

Five methods were used to study the thermo-oxidative degradation of siloxane-containing polyimide (polysiloxaneimide, PSI), and the results were compared with unmodified polyimide. The degradation of PSI was found to be a complex process composed of at least two overlapping stages for which apparent activation energies can be calculated. These investigated methods were those of Kissinger, Van Krevelen, Horowitz-Metzger, Coats-Redfern, and MacCallum-Tanner. These methodologies evaluated the different apparent activation energies E-a, and the single heating rate techniques proved more precise. The E-a of the imide segments in PSI was larger than that in PI. The result may be rationalized on the basis of the formation of thermally stable structures. (C) 1998 Elsevier Science Limited. All rights reserved.