Preparation of the modified epoxy resins with flexible diglycidyl ether of diethylene glycol

Lot of efforts have been devoted to improve the toughness and ductility of diglycidyl ether of bisphenol-A (DGEBA) epoxy resin (EP), which limit its wide applications in many industry fields. In this study, reactive modifier diglycidyl ether of diethylene glycol (DGEG) with low viscosity has been synthesized and introduced to the EP by solvent-free processing. The mechanical properties of the modified EPs are studied via the tensile and impact test. The results show that the incorporation of flexible DGEG chains into EPs improves the elongation and impact strength. Interestingly, the tensile strength can be improved by a reasonable content of flexible DGEG. It is concluded that the addition of a selected amount of DGEG, namely 14-28 wt%, can simultaneously strengthen and toughen DGEBA EPs. The subsequent impact-fractured surfaces are observed using scanning electron microscopy, and the results are well consistent with those obtained from the impact test. Thermogravimetric analysis shows that the thermal stability slightly decreases with the increase of DGEG. Finally, the differential scanning calorimetry shows that the glass transition temperature (T-g) decreases slightly with increasing the flexible DGEG content. The presence of a single T-g reveals that the DGEG/epoxy composite has a homogeneous phase structure.