Simultaneous monitoring of the imidization and cure reactions of LaRC PETI-5 sized on a braided glass fabric substrate by dynamic mechanical analysis

The imidization and cure reactions of a thin film of phenylethynyl imide ol igomer (LaRC PETI-5, M-n = 2500 g/mol) applied to a glass fabric and proces sed under cumulative and isothermal heat-treatment conditions have been mea sured. Three distinguishable peaks were detected in the tan delta curves, w hich give useful information on the glass transition temperature, imidizati on temperature, and cure reaction temperature. The degree of imidization or cure reaction occurring during the cumulative and isothermal cure processe s is related to the presence and size of the imidization peak and the cure reaction peak. The rate of cure increases substantially above 250 degreesC. The T-g of the fully cured LaRC PETI-5 was measured as 287 degreesC. The m aximum in the tan delta curve transformed with increasing cure temperature from a tripler due to completion of imidization above 250 degreesC to a sin glet after completion of the cure reaction. The maximum of the singlet tan delta curve at 287 degreesC is identified as the T-g of the LaRC PETI-5 pol yimide. It is concluded that the dynamic mechanical behavior of LaRC PETI-5 strongly depends on thermal history, especially above 300 degreesC. This r esult also confirms that after cumulative or isothermal processing, LaRC PE TI-5 can be fully cured at 350 degreesC for 1 h. These results agree well w ith the Fourier Transform infrared spectroscopy and differential scanning c alorimetry results reported earlier. (C) 2001 Published by Elsevier Science Ltd.