| In our present work, we took a new in-situ toughening method by using liquid crystalline epoxy to improve the toughness of epoxy resin.A novel liquid crystalline epoxy resin 4-epoxypropoxy phenyl-4?epoxypropxy benzoate (PHBHQ) was synthesized. The phase behaviours, curing character of PHBHQ reacted with 4,4?diaminodiphenylmethane(DDM) or mixed aromatic diamine [DDMIDDS(4,4?diaminodiphenylsulfone)/DDE(4,4?diaminodiphenyl ester)=512/ 1 wt ratio] were characterized by Differential Scanning Calorimetry (DSC) and Polarized Optical Microscopy(POM). The results indicated that PHBHQ showed nematic phase duiing cooling process between 1310C and 940C.The curing mechanism and kinetics of PHBHQ reacted with DDM were studied by Flourier Transmit Infrared (FTIR). The curing reaction proceeded in auto-accelerating mechanism and was accelerated by the hydroxyl group produced in the curing process. The kinetics parameters of each step of curing reaction were calculated: Ea1=:66.5 1KJ/mol, lnA1=6.65, Ea2= 69.O5KJ/mol, lnA2?.34.PHBHQ was used to toughen bisphenol-A diglycidyl (E-5 1 resin). Mechanical characterization and thermal property were greatly increased by using curing agent of mixed aromatic diamine , the impact strength and glass transition temperature of E-5 1 resin modified by 5Owt% PHBHQ were 40.2KJIm2 and I 82.90C respectively. Studies using Scanning Electronic Microscopy (SEM), Wide-angle X-Ray Diffraction(WAXD) and Dynamic Thermomechanical Analysis(DMTA) showed the formation of two-phase structure with oriental ordered mesogenic domain which can initiate, branch, terminate the crack dispersed in the continuous epoxy matrix. |
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