A Tetrafunctional yet Low-Viscosity Glycidylamine Modifier for DGEBA Epoxy Resins

Abstract

Improving the thermal performance of bisphenol A-based epoxy resin (DGEBA) without compromising its processability is a persistent challenge, primarily due to the inherent viscosity–functionality trade-off in multifunctional epoxy resins. In this work, a low-viscosity tetrafunctional glycidylamine epoxy resin (DETGA) with a high-epoxy-value (0.80 mol per 100 g) was synthesized from diethyltoluenediamine and epichlorohydrin via an industrially feasible two-step ring-opening and cyclization process using a phase-transfer catalyst. The incorporation of DETGA into DGEBA systems significantly enhanced the crosslinking density of the cured network. Consequently, the modified epoxy systems exhibited simultaneously improved thermal and mechanical properties while retaining good processability. Specifically, the glass transition temperature increased progressively with DETGA content, showing a maximum increase of 28.2 °C at 20 wt% loading, alongside notable enhancements in tensile, flexural, and impact strength. Non-isothermal curing kinetics analysis indicated a reduced apparent activation energy, confirming the role of DETGA in promoting the curing reaction. This study demonstrates an effective molecular design strategy to achieve multifunctional epoxy resins that combine high thermal performance with low viscosity.