Synthesis of polyfunctional amines as curing agents and its effect on mechanical property of epoxy polymers

A curing agent is required to cure an epoxy resin, but a few curing agents also improve the mechanical properties of the resin. In addition, it is rare to find hardeners containing multiple amines, which can be used to form high crosslink densities. In this study, two different curing agents with six amine functional groups each were synthesized via a two‐step reaction. In the first step, isophorone diamine (IPDI) was reacted with two equivalents of pentaerythritol triacrylate (PETA). The resulting IPDI‐PETA2 was reacted with ethylene diamine and 4,4′‐diaminodiphenyl sulfone to form two amine curers with six amines each—IPDI‐PETA2‐ED (ED) and IPDI‐PETA2‐DDS (DDS). Both amines were added in varying amounts to an epoxy composition consisting of dicyandiamide and 2‐methylimidazole to improve the mechanical properties compared with a reference epoxy composition. Mechanical studies showed that an epoxy composition containing 5% IPDI‐PETA2‐DDS improved the flexural strength by 34% and impact strength by 36.7%. Furthermore, adding 5% IPDI‐PETA2‐ED to the epoxy composition increased the flexural strength by 39.7%, to 197 MPa and the impact strength by 38.8% to 68 J/m. These results highlight the potential of curing agents containing multiple amines for improving the mechanical properties of epoxy resins.