There has been an exponential rise in the interest for waterborne polyurethanes (WBPU), due to the easy customizability of their properties and their ecofriendly nature. Moreover, their aqueous state facilitates the incorporation of hydrophilic reinforcements. Cellulose nanofibers (CNFs) have shown great potential, thanks to their renewability, large natural availability, low cost and great specific properties. However, CNFs often require some modification to obtain optimal compatibility. In this work, standard bleached hardwood kraft pulp has been subjected to a carboxylation process followed by mechanical disintegration. Varying treatment times and passes, CNF samples with different carboxylation degrees have been obtained. WBPU/CNF nanocomposites with different CNF content have been prepared. The effect of the carboxylation degree on the CNFs and on the nanocomposites properties has been studied. Although carboxylation damaged the cellulose structure, decreasing the crystallinity degree of CNF and reducing the thermal stability of fibers, composites showed better thermal and thermomechanical stability and improved mechanical properties than the unreinforced matrix counterpart. A maximum increase of 1670% in modulus, 377% in stress at yield and 86% in stress at break has been achieved for composites reinforced with carboxylated fibers. Therefore, it was observed that carboxylation improved matrix/reinforcement interactions.

由于水性聚氨酯（WBPU）的特性易于定制且具有环保特性，因此其兴趣呈指数增长。而且，它们的水状态促进了亲水性增强剂的结合。纤维素纳米纤维（CNFs）由于其可更新性，大自然可用性，低成本和出色的特殊性能而显示出巨大的潜力。但是，CNF通常需要进行一些修改才能获得最佳兼容性。在这项工作中，对标准的漂白硬木牛皮纸浆进行了羧化处理，然后进行机械分解。通过改变处理时间和通过次数，可以获得具有不同羧化度的CNF样品。制备了具有不同CNF含量的WBPU / CNF纳米复合材料。研究了羧化度对CNFs和纳米复合材料性能的影响。尽管羧化作用破坏了纤维素的结构，降低了CNF的结晶度并降低了纤维的热稳定性，但复合材料与未增强的基质相比，表现出更好的热稳定性和热机械稳定性，并改善了机械性能。对于用羧化纤维增强的复合材料，最大模量增加了1670％，屈服应力增加了377％，断裂应力增加了86％。因此，观察到羧化改善了基质/增强相互作用。与未增强的基质相比，这种复合材料表现出更好的热和热机械稳定性，并改善了其机械性能。对于用羧化纤维增强的复合材料，最大模量增加了1670％，屈服应力增加了377％，断裂应力增加了86％。因此，观察到羧化改善了基质/增强相互作用。与未增强的基质相比，这种复合材料表现出更好的热和热机械稳定性，并改善了其机械性能。对于用羧化纤维增强的复合材料，最大模量增加了1670％，屈服应力增加了377％，断裂应力增加了86％。因此，观察到羧化改善了基质/增强相互作用。