Key Laboratory of Carbon Fiber and Functional Polymers, Ministry of Education, Beijing University of Chemical Technology, Beijing 100029, China.
Beijing Engineering Research Center of Synthesis and Application of Waterborne Polymer, Beijing University of Chemical Technology, Beijing 100029, China.
Molecules. 2022 Nov 5;27(21):7588. doi: 10.3390/molecules27217588.
The comprehensive balance of the mechanical, interfacial, and environmental requirements of waterborne polyurethane (WPU) has proved challenging, but crucial in the specific application as the binder for high-performance polymer fiber composites. In this work, a multi-step chain extension (MCE) method was demonstrated using three kinds of small extenders and one kind of macro-chain extender (CE) for different chain extension steps. One dihydroxyl blocked small molecular urea (1,3-dimethylolurea, DMU) was applied as one of the CEs and, through the hybrid macrodiol/diamine systems of polyether, polyester, and polysiloxane, the WPU was developed by the step-by-step optimization on each chain extending reaction via the characterization on the H-bonding association, microphase separation, and mechanical properties. The best performance was achieved when the ratio of polyether/polyester was controlled at 6:4, while 2% of DMU and 1% of polysiloxane diamine was incorporated in the third and fourth chain extension steps, respectively. Under the condition, the WPU exhibited not only excellent tensile strength of 30 MPa, elongation of break of about 1300%, and hydrophobicity indicated by the water contact angle of 98°, but also effective interfacial adhesion to -aramid fabrics. The peeling strength of the joint based on the polysiloxane incorporated WPU after four steps of chain extension was 430% higher than that prepared through only two steps of chain extension. Moreover, about 44% of the peeling strength was sustained after the joint had been boiling for 40 min in water, suggesting the potential application for high-performance fabric composites.
水性聚氨酯（WPU）的机械、界面和环境要求的综合平衡一直具有挑战性，但在特定应用中作为高性能聚合物纤维复合材料的粘合剂却至关重要。在这项工作中，使用三种小分子扩链剂和一种大分子扩链剂（CE）进行了多步链扩展（MCE）方法，用于不同的链扩展步骤。一种二羟甲基封端小分子尿素（1,3-二甲基脲，DMU）被用作 CE 之一，并通过聚醚、聚酯和聚硅氧烷的混合大二醇/二胺体系，通过逐步优化每个链延伸反应，通过氢键缔合、微相分离和机械性能的表征，开发了 WPU。当聚醚/聚酯的比例控制在 6:4 时，性能最佳，而在第三和第四链延伸步骤中分别加入 2%的 DMU 和 1%的聚硅氧烷二胺。在这种条件下，WPU 不仅表现出优异的拉伸强度 30 MPa、断裂伸长率约 1300%和水接触角为 98°表示的疏水性，而且还与-aramid 织物具有有效的界面附着力。经过四步链延伸的含硅氧烷 WPU 接头的剥离强度比仅经过两步链延伸的制备的剥离强度高 430%。此外，在水中煮沸 40 分钟后，接头仍能保持约 44%的剥离强度，这表明其在高性能织物复合材料中有潜在的应用。
