Curing and Thermal Properties of PEPEB Liquid Crystalline Diepoxide/Aromatic Diamine

Abstract

The liquid crystalline epoxy resin p-phenylene di[4-2-(2,3-epoxypropyl)ethoxy] benzoate (PEPEB) was synthesized. The curing behavior of the liquid crystalline epoxy resin (LCER) with 4,4-diaminodiphenylmethane (DDM) was studied by fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and torsional braid analysis (TBA). Morphology of curing product was observed by polarized optical microscopy (POM) at different temperatures. Nonisothermal curing kinetics of this system were investigated by DSC. Results show that the PEPEB has a smectic liquid crystalline structure, and the melting point, T m, is 119°C, the clearing point is 184°C. The cured-system's gel point, T I , is 83.5°C; cure temperature, T P , is 111.6°C; and the disposal temperature, T f , is 145.8°C; activation energy of curing reaction is 4.84 KJ/mol. Observation by POM shows that with the upgrade of initial curing temperature, the filament structure of this system transferred from anisotropy to isotropy.