Preparation and Curing Kinetics Investigation of Diglycidyl Ether of Bisphenol A/Liquid Crystalline Epoxy Resin Blends

摘要

A novel liquid crystalline epoxy resin (PHQEP) was synthesized by phase transfer catalytic method and characterized as a nematic liquid crystalline by polarized optical microscope (POM). The cure kinetics of diglycidyl ether of bisphenol A (E-51 )/PHQEP blends using 4,4'-diaminodiphenylsulphone (DDS) as the curing agent was studied by non-isothermal differential scanning calorimetry (DSC) at four linearly programmed heating rates of 5, 10, 15, and 20 K/min. The apparent activation energy (E_a) was determined by Friedman method, and kinetic model was predicted by Malek method. In the curing process of PHQEP/DDS, the E_a values decreased slowly with the conversion in the region of 0.2～0.5 for the formation of liquid crystalline phase. The E_a value of PHQEP/DDS system is generally higher than those of PHQEP/E-51/DDS and E-51/DDS systems and the E_a of PHQEP/E-51/DDS system is generally higher than that of E-51/DDS. This may imply that PHQEP is less reactive than E-51 in the curing process, since the molecular movement was limited because of the aromatic ester structure and the hydrogen bonds which were formed between the carbonyl groups of PHQEP and hydroxyl groups produced in the curing process. Furthermore, autocatalyt-ic model was predicted to be the kinetic model of the above mentioned three systems. The predicted curves fit well with the experimentally obtained curves.