Development of sustainable biobased fibers is required to displace their fossil-based counterparts, e.g., in textile, nonwoven, or composite applications. Regenerated protein fibers have a potential in this regard if their mechanical properties are improved. Herein, we study for the first time the use of nanocellulose as reinforcement in regenerated protein fibers produced using wet spinning. The influence of cellulose nanocrystals (CNC) incorporated into regenerated casein fibers is examined in terms of mechanical and morphological properties. The influence of different conditions for fiber chemical cross-linking is also investigated. Incorporation of CNC (up to 37.5 wt %) into spin dopes results in a continuous increase of fiber Young’s modulus (up to twofold) in the dry state. Both maximum and breaking tenacity of dry fibers are enhanced by CNC, with a maximum at 7.0–10.5 wt % of CNC. When testing after being wetted, both breaking tenacity and Young’s modulus of the composite fibers decrease, likely due to weakening of hydrogen bonds between CNC in the presence of water. We also demonstrate that the presence of salt during chemical cross-linking is crucial to produce intact and separated fibers in the yarn.

中文翻译：

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通过湿纺法再生酪蛋白-纳米纤维素复合纤维

需要开发可持续的生物基纤维来替代其基于化石的对应物，例如在纺织，非织造布或复合材料应用中。如果它们的机械性能得到改善，则再生蛋白质纤维在这方面具有潜力。在本文中，我们首次研究了纳米纤维素在湿纺生产的再生蛋白纤维中的增强作用。从机械和形态学方面研究了掺入到再生酪蛋白纤维中的纤维素纳米晶体（CNC）的影响。还研究了不同条件对纤维化学交联的影响。在纺丝原液中掺入CNC（最多37.5 wt％）会导致在干燥状态下纤维杨氏模量不断增加（最多两倍）。CNC增强了干纤维的最大韧性和断裂韧性，含量最高为CNC的7.0–10.5 wt％。润湿后进行测试时，复合纤维的断裂强度和杨氏模量都会降低，这可能是由于存在水时CNC之间的氢键减弱所致。我们还证明了化学交联过程中盐的存在对于在纱线中产生完整且分离的纤维至关重要。