Effect of type of substitution in 4,4′-bis-(diaminodiphenyl) methane hardener on cure kinetics, mechanical, and flame retardant properties of tetrafunctional epoxy resins

The nature of the substituent in 4,4'-bis-(diaminodiphenyl) methane (DDM) hardener on the cure kinetics, mechanical, and flame retardant properties of N,N,N',N'-tetraglycidyl diaminodiphenyl methane (TGDDM) resin is investigated in comparison with unsubstituted DDM and widely used 4,4'-bis-(diaminodiphenyl) sulfone hardeners. Dynamic differential scanning calorimetry (DSC) and cure rheology studies showed that the substitution decreased the reactivity of the amine. An electron-withdrawing chlorine substituent was found to be more effective than an electron-releasing methyl group in reducing the amine reactivity. Substituted and unsubstituted DDM hardeners showed two peaks in their DSC thermograms that were due to steric hindrance in the former and deficiency of amine in the latter. Substitution showed its effect on the mechanical properties and glass-transition temperature. The flexural modulus was increased; however, the Izod impact and glass-transition temperature were decreased in substituted amine systems. The limiting oxygen index results showed higher flame retardancy in the chlorine substituted hardener system compared to other hardener systems that were studied. (c) 2006 Wiley Periodicals, Inc.