A STUDY OF THE THERMAL CURE OF A PHENYLETHYNYL-TERMINATED IMIDE MODEL-COMPOUND AND A PHENYLETHYNYL-TERMINATED IMIDE OLIGOMER (PETI-5)

The kinetic mechanism of the thermal cure of a phenylethynyl-terminate d imide model compound, 3,4'-bis[(4-phenylethynyl)phthalimido] dipheny l ether (PEPA-3,4'-ODA) and a phenylethynyl-terminated imide oligomer PETI-5 (MW 5000 g/mol) was studied. FTIR was used to follow the cure o f the model compound, while thermal analyses (DSC) was used to follow the cure of the PETI-5 oligomer. The changes in IR absorbance of pheny lethynyl triple bonds at 2214 cm(-1) of PEPA-3,4'-ODA as a function of cure time were detected at 318, 336, 355, and 373 degrees C, respecti vely. The changes in the glass transition temperature, T-g, of PETI-5 as a function of time were measured at 350, 360, 370, 380, and 390 deg rees C, respectively. The DiBenedetto equation was applied to define t he relative extent of cure, x, of the PETI-5 oligomer by T-g. For the model compound, the reaction followed first order kinetics, yielding a n activation energy of 40.7 kcal/mol as determined by infrared spectro scopy. For PETI-5, the reaction followed 1.5th order, yielding an acti vation energy of 33.8 kcal/mol for the whole cure reaction, as determi ned by T,using the DiBenedetto method. However, the cure process of PE TI-5 just below 90% by this method followed first-order kinetics yield ing an activation energy of 37.2 kcal/mol. (C) 1998 John Wiley & Sons, Inc.