The curing reaction of poly(ether‐sulfone)‐modified epoxy resin

One of the useful methods to improve the toughness of epoxy resin is by mixing the resin with poly(ether-sulfone) (PES). In the present work, two hydroxyl-terminated PESs with molecular weights M n = 28600 and 4200 were used for blending with epoxy resin. The curing reaction of diglycidyl ether/bisphenol-A (DGEBA) with 4,4'-diaminodiphenyl sulfone (DDS) in the presence of hydroxyl-terminated PES was studied by means of differential scanning calorimetry (DSC) and gel-permeation chromatography (GPC). For the DGEBA-DDS-PES system with a stoichiometric ratio of epoxy and amino groups the DSC experimental results showed that at a fixed molecular weight of PES the curing reaction rate decreases with increasing PES concentration. At a fixed PES concentration (in the range of between 0 and 20 wt.-% of PES), the DGEBA-DDS system modified with hydroxyl-terminated PES with lower molecular weight had a faster curing reaction rate at low conversion and a slower curing reaction rate at high conversion. The GPC results showed the evidence of etherification between low-molecular-weight PES with epoxy resin. However, very little etherification of high-molecular-weight hydroxyl-terminated PES with epoxy resin was found. Based on the experimental results, a curing reaction mechanism of DGEBA with DDS in the presence of hydroxyl-terminated PES is proposed.