Decomposition mechanisms and kinetics of amine/anhydride-cured DGEBA epoxy resin in near-critical water

Abstract

The decomposition behaviour of diglycidylether of bisphenol A (DGEBA) cured with 4-methyl tetrahydrophthalic anhydride (MeHHPA) or dapsone (DDS) in near-critical water was investigated. Reaction mechanisms based homolysis of the bonds in the polymer followed by saturation of the resulting radicals by hydrogen abstraction from the water were discussed. The decomposition rate increased with the increase of reaction time and temperature. Due to the presence of ester groups in the DGEBA/MeHHPA/BDMA main chains, they were broken at the beginning of the decomposition process, while it was more difficult to decompose the DGEBA/DDS system, due to the introduced benzene ring. The GC-MS proved that the two resin systems were decomposed to small molecular compounds. The experimental results indicated that the decomposition mechanisms of the two resin systems might involve cyclization reactions and chain-end scission in near-critical water. The two resin systems tended to form oligomers with longer molecular chains at lower temperatures with the random scission. Meanwhile, a first-order kinetic model was implemented for the decomposition reaction process. The results showed that the calculated activation energy (E_a) of the two resin systems was 266.7 kJ mol⁻¹ and 170.7 kJ mol⁻¹, respectively.