Waterborne polyurethane (WPU) has gained widespread attention. However, conventional linear WPU emulsions have lower mechanical properties, poor water resistance, and other disadvantages. In this study, polyurethane prepolymers containing branched chains were successfully synthesized by using diphenylmethane diisocyanate (MDI), polytetramethylene ether glycol (PTMG) and castor oil (CO) as the main raw materials. On this basis, epoxy resin was used to further modify the obtained polyurethane prepolymers, which results in an increase in mechanical properties, water resistance, and heat resistance due to the formation of a network cross-linked structure during the film formation. The type and addition amount of epoxy resin were determined by centrifugal stability and particle size of WPU emulsions, water absorption, and mechanical properties of WPU films. The results showed that the prepared epoxy resin–modified WPU (EWPU) emulsions have excellent centrifugal stability. If 7% epoxy resin was added after the polyurethane chain expansion, the corresponding EWPU films have good mechanical properties (the tensile strength of 28.7 MPa and the elongation at break of 379%), water resistance (water absorption of 4.21%), and the thermal stability due to the cross-linked structure in EWPU. This kind of EWPU emulsions may have promising applications in coating material, adhesives, and the textile industry.

水性聚氨酯（WPU）受到广泛关注。然而，传统的线性WPU乳液存在机械性能较低、耐水性差等缺点。本研究以二苯甲烷二异氰酸酯（MDI）、聚四亚甲基醚二醇（PTMG）和蓖麻油（CO）为主要原料，成功合成了含支链的聚氨酯预聚物。在此基础上，采用环氧树脂对所得聚氨酯预聚物进行进一步改性，由于成膜过程中形成网状交联结构，从而提高了机械性能、耐水性和耐热性。根据WPU乳液的离心稳定性和粒径、吸水率、WPU 薄膜的力学性能。结果表明，所制备的环氧树脂改性WPU（EWPU）乳液具有优异的离心稳定性。若聚氨酯扩链后添加7%环氧树脂，则相应的EWPU薄膜具有良好的力学性能（拉伸强度28.7 MPa，断裂伸长率379%）、耐水性（吸水率4.21%）、 EWPU 中的交联结构带来热稳定性。这种EWPU乳液在涂料、粘合剂和纺织工业中可能具有广阔的应用前景。相应的EWPU薄膜具有良好的机械性能（拉伸强度为28.7 MPa，断裂伸长率为379%）、耐水性（吸水率为4.21%），并且由于EWPU中的交联结构而具有良好的热稳定性。这种EWPU乳液在涂料、粘合剂和纺织工业中可能具有广阔的应用前景。相应的EWPU薄膜具有良好的机械性能（拉伸强度为28.7 MPa，断裂伸长率为379%）、耐水性（吸水率为4.21%），并且由于EWPU中的交联结构而具有良好的热稳定性。这种EWPU乳液在涂料、粘合剂和纺织工业中可能具有广阔的应用前景。