Isothermal curing analysis and properties of ultra heat-resistant polyimide composites by DMA method

The isothermal curing process of T700 carbon fiber/P450 polyimide prepreg is characterized by dynamic mechanical analysis method and the gelation points are analyzed by torsional braid analysis theory. The growth mechanisms of the mechanical property at different constant temperatures are investigated by the relative mechanical growth rate of storage modulus and the curing kinetics models are established. The theories of Flory and Hsich are used to calculate the activation energy during the curing reaction of prepreg. The results indi-cates that the gelation times which are detected by the method of torsional braid analysis at 300, 310, 330, and 350 degrees C were 293.7, 213.8, 104.1, and 45.4 min, respectively. The activation energies of curing reaction are calculated by Flory theory and Hsich theory, they are 112.35 and 119.96 kJ/mol, respec-tively. The feasibly of curing system 300 degrees C x 4 h + 330 degrees C x 2 h + 350 degrees C x 2 h + 370 degrees C x 2 h is verified by the mechanical properties and the heat resistance of polyimide composite.