Preparation, Curing and Properties of Hydantoin Based Epoxy Resins with Different Structures

Abstract

AbstractHydantoin based epoxy resins are a kind of special epoxy resin with nitrogen‐containing five‐membered heterocycle structure but less intensively studied than the common bisphenol A type epoxy resins. Besides, only 5,5‐dimethylhydantoin epoxy resin (DMHR) was paid enough attention among hydantoin based epoxy resins. To understand the reasons behind the above background, in this work, three hydantoin based epoxy resins with different structures but similar epoxy values (0.37–0.40 mol/100 g), including hydantoin epoxy resin (HR), 5,5‐dimethylhydantoin epoxy resin (DMHR), 1,3‐dihydroxymethyl‐5,5‐dimethylhydantoin epoxy resin (DHMDMHR), were synthesized first, their non‐isothermal curing kinetics, thermal and mechanical properties and adhesion performance of the cured products were then investigated and compared with bisphenol A epoxy resin E44. The apparent activation energies of the three hydantoin based epoxy resin/diaminodiphenylmethane (DDM) systems were in the range of 55–59 kJ/mol, slightly higher than that of E44/DDM system (47.1 kJ/mol). The properties of the three cured hydantoin based epoxy resins, such as glass transition temperature, thermal stability, tensile strength and storage modulus, declined with decreasing content of the hydantoin cycles. 5,5‐dimethylhydantoin epoxy resin (DMHR) had the highest adhesion strength (5.6 MPa) among the three hydantoin based epoxy resins, but nearly 60 % lower than that of bisphenol A type E44 epoxy resin (13.2 MPa) when a polyether amine was used as the curing agent. The cured product of E44 epoxy resin was stronger, tougher and thermally more stable than the cured products of the three hydantoin based epoxy resins. While, hydantoin based epoxy resins exhibited superior damping performance than E44 epoxy resin.