Preparation of Terminal Isocyanate-Based Polyurethane Prepolymer and Its Toughening and Modification of Epoxy Resin

To improve the performance of epoxy resin (EP), this study selected hexamethylene diisocyanate trimer (HDI trimer) and polypropylene glycol (PPG1000) as the main raw materials. Through a simple addition reaction, a terminal isocyanate group (-NCO) polyurethane prepolymer (PUP) was successfully synthesized. A grafting reaction with EP was then carried out to prepare a series of epoxy resin grafted interpenetrating polymer network (IPN) polymers (EP-PUP-n) modified by the polyurethane prepolymer. The effect of PUP on the material properties was investigated. According to the results of mechanical performance tests, when the PUP content reached 20 phr, the impact strength and elongation at break of the EP-PUP-20 material increased by 128.1% and 43.1%, respectively, compared to pure EP material. Meanwhile, its tensile strength and bending strength remained at levels of 68.8 and 102.3 MPa, respectively. Thermogravimetric analysis shows that PUP-EP-n has excellent thermal stability. This opens up new avenues for the use of epoxy resins in various fields.