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

摘要

The imidization and cure reactions of a thin film of phenylethynyl imide oligomer (LaRC PETI-5,N_n=2500g/mol) applied to a glass fabric and processed under cumulative and isothermal heat-treatment ocnditions have been measured.Three distinguishable peaks were detected in the tan #delta# curves,which give useful information on the glass transition temperature,imidization temperature,and cure reaction temperature.The degree of imidization or cure reaction occurring furing the cumulative and isothermal cure processes is related to the presence and size of the imidization peak and the cure reaction peak.The rate of cure increases substantially above 250degC.The T_g of the fully cured LaRC PETI-5 was measured as 287degC.The maximum in the tan #delta# curve transformed with increasing cure temperature from a triplet due to completion of imidization above 250degC to a singlet after completion of teh cure reaction.The maximum of the singlet tan #delta# curve at 287degC is identified as the T_g of the LaRC PETI-5 polyimide.It is concluded that the dynamic mechanical behavior of LaRC PETI-5 strongly depends on thermal history,especially above 300degC.This result also confirms that after cumulative or isothermal rocessing,LaRC PETI-5 can be fully cured at 350degC for 1 h.These results agree well with the Fourier Transform infrared spectroscopy and differential scanning calorimetry results reported earlier.