THERMOOXIDATIVE DEGRADATION OF SILOXANE-CONTAINING POLYIMIDE AND UNMODIFIED POLYIMIDE

Five methods were used to study the thermo-oxidative degradation of si loxane-containing polyimide (polysiloxaneimide, PSI), and the results were compared with unmodified polyimide. The degradation of PSI was fo und to be a complex process composed of at least two overlapping stage s for which apparent activation energies can be calculated. These inve stigated methods were those of Kissinger, Van Krevelen, Horowitz-Metzg er, Coats-Redfern, and MacCallum-Tanner. These methodologies evaluated the different apparent activation energies E-a, and the single heatin g rate techniques proved more precise. The E-a of the imide segments i n PSI was larger than that in PI. The result may be rationalized on th e basis of the formation of thermally stable structures. (C) 1998 Else vier Science Limited. All rights reserved.