Eco-Friendly Epoxy-Terminated Polyurethane-Modified Epoxy Resin with Efficient Enhancement in Toughness.

Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and using solvents during the preparation of polyurethane-modified epoxy resins. To address these issues, in this study, we reported a facile and green approach for preparing epoxy-terminated polyurethane (EPU)-modified epoxy resins with different EPU contents. It was found that the toughness of the epoxy resin was significantly improved after the addition of EPU. When the EPU content was 30 wt%, the elongation at break and toughness were improved by 358.36% and 73.56%, respectively. In comparison, the toughening effect of EPU outperformed that of ITPU. Moreover, the high content of EPU did not significantly decrease the glass transition temperature and had little effect on the thermal stability of the epoxy resin.