Abstract:Isocyanate can be used as hardener of epoxy resin. The curing process was studied by comparing the
differences of the final structures under different curing conditions. Altering the molar ratio of isocyanate to epoxide
groups, the changes of structure during curing and final properties of the cured materials were investigated by using
FTIR/ ATR,differential scanning calorimetry(DSC),dynamic thermal mechanical analysis(DMTA) and so on. As the
results indicated, the curing process of epoxy/ isocyanate formulations can be divided into three stages in order of increasing
temperature. Trimerization of isocyanate took place at first. And the following stages are a complex process:oxazolidone
rings are prepared by Isocyanate and epoxy resin firstly. Trimerization of isocyanate took place among the oligomers
terminated by isocyanate groups with oxazolidone rings as linear chain extenders. Oxazolidone rings were prepared
by isocyanurates and remanent epoxy resin at the last stage. And the transition between oxazolidone rings and
isocyanurate rings is a reversible process. Different structures ascribed to initial ratios lead to the different performances.
When I/ E=1. 8, the isocyanate/ epoxy resin/ glass fiber formulation composition appeared a good comprehensive
mechanical property. The bending strength,bending modulus and interlaminar shear strength of the isocyanate/ epoxy
resin/ glass fiber formulation composition are 652. 53 MPa,3 3270. 63 MPa,31. 66 MPa,respectively,better than
those MeHTPA/ epoxy resin/ glass fiber composites. When I/ E=2. 0,the Tg reached 305℃,higher than the temperature
of traditional epoxy resin curing formulations,obviously.
