Curing Kinetics and Thermal Properties of Liquid Crystalline p-PEPB/Bisphenol-A Epoxy/Diamine System

The curing kinetics of bisphenol-A epoxy resin (BPAER) modified by liquid crystallinep-phenylene di-[4-(2,3-epoxypropyl) benzoate] (p-PEPB), with a diaminesuch as 4,4′-diaminodiphenyl ether (DDE) as a curing agent, was investigated bynon-isothermal DSC method. The correlation between apparent activation energy, Ea,and the conversion, α, was obtained by Ozawa method. The catalyzed effect ofhydroxyl groups was determined in DSC experiment and a molecular reactionmechanism was proposed. The results show that hydroxyl groups can accelerate thecuring reaction and lower the Ea value. The average values of Ea for p-PEPB/DDE andBPAER/p-PEPB/DDE systems are 122.4 and 72.28 kJ.mol-1, respectively. There is aphase separation in the curing process with LC phase formation. These curingreactions can be described by the model of Sestak and Berggren (S-B model). Theaverage reaction orders, i.e., m and n for p-PEPB/DDE system are 0.64 and 1.26 andfor BPAER/p-PEPB/DDE system are 0.48 and 1.35, respectively. The dynamicmechanical loss peak temperature is about 14°C higher than that of pure BPAERsystem when the content of p-PEPB is 5 wt%.