Cellulose nanocrystal (CNC) based composites have been explored as protective organic coatings for metal surfaces, ceramics, and wood. However, the inherent hygroscopic nature of CNCs hinders the technology from being utilized on an industrial scale as water uptake can result in soft, weak coatings. Herein, a moisture-resistant nanocomposite coating was prepared from CNCs in water and a waterborne blocked polyisocyanate (PIC). The cure temperature, which controls isocyanate deblocking and therefore cross-linking of the composite, was investigated across a wide temperature range (25–150 °C), and the subsequent films were characterized in terms of water contact angle, hygroscopic strain, and coating mechanical properties. Water contact angle measurements revealed a remarkable 3-fold reduction in hydrophilicity by cross-linking CNC with PIC. The hygroscopic strain was reduced by 20 orders of magnitude compared to untreated CNCs at 90% relative humidity (RH), which is also evidenced by static moisture sorption studies showing only a 7% moisture uptake. The mechanical and optical properties of the CNC/PIC nanocomposites were investigated to determine the physical performance of the coated material. Finally, the nanocomposite coatings exhibited a reversible humidity-dependent color change. The humidity response of these materials is potentially useful in humidity sensor applications.

中文翻译：

---

基于嵌段异氰酸酯和纤维素纳米晶体（CNC）作为多元醇的高性能水性聚氨酯涂料

纤维素纳米晶体（CNC）基复合材料已被研究用作金属表面，陶瓷和木材的保护性有机涂层。然而，CNCs固有的吸湿性阻碍了该技术在工业规模上的应用，因为吸水会导致柔软，薄弱的涂层。本文中，由CNC控制器在水中和水性封端多异氰酸酯（PIC）中制备了防潮纳米复合涂层。在很宽的温度范围内（25-150°C）研究了控制异氰酸酯解封并因此控制复合材料交联的固化温度，随后的膜在水接触角，吸湿应变和涂层方面进行了表征机械性能。水接触角测量结果表明，通过将CNC与PIC交联，亲水性显着降低了3倍。与未经处理的CNC在90％相对湿度（RH）下相比，吸湿应变降低了20个数量级，这也由静态吸湿研究表明，吸水率仅为7％。研究了CNC / PIC纳米复合材料的机械和光学性能，以确定涂层材料的物理性能。最后，纳米复合涂层表现出可逆的湿度依赖性颜色变化。这些材料的湿度响应在湿度传感器应用中可能很有用。研究了CNC / PIC纳米复合材料的机械和光学性能，以确定涂层材料的物理性能。最后，纳米复合涂层表现出可逆的湿度依赖性颜色变化。这些材料的湿度响应在湿度传感器应用中可能很有用。研究了CNC / PIC纳米复合材料的机械和光学性能，以确定涂层材料的物理性能。最后，纳米复合涂层表现出可逆的湿度依赖性颜色变化。这些材料的湿度响应在湿度传感器应用中可能很有用。