Fibre and Polymer Technology, KTH Royal Institute of Technology, SE-10044 Stockholm, Sweden.
Biomacromolecules. 2020 Apr 13;21(4):1480-1488. doi: 10.1021/acs.biomac.0c00040. Epub 2020 Mar 13.
Cellulose nanofibrils (CNFs) prepared from wood biomass are promising candidates to replace oil-based materials in, for example, packaging applications. However, CNFs' affinity for water combined with their small size leads to very slow and energy-demanding processes for handling and removal of water. To a large extent, this is the major roadblock that prevents a feasible production of dry CNF-based materials on an industrial scale. In this work, self-fibrillating fibers (SFFs) from wood, where the fibrils can be liberated by external stimuli, were prepared via sequential TEMPO and periodate oxidation reactions. Papers made from these modified fibers using conventional laboratory papermaking methods were then in situ nanofibrillated via a modest pH increase. With a dewatering time of less than 10 s for a 3 g/L dispersion, SFFs represent a major improvement over conventional CNF nanopapers that take approximately 6 h to dewater. Moreover, 100 g/m nanopapers obtained through in situ fibrillation exhibited comparable, if not superior, properties to those reported for conventionally made CNF films. A tensile strength of 184 MPa, a Young's modulus of 5.2 GPa, a strain at break of 4.6%, 90% optical transmittance, and an oxygen permeability of 0.7 cm μm m d kPa at 50% RH were measured for SFF nanopapers. Furthermore, in situ nanofibrillation of the SFFs can also be achieved from already dried papers, facilitating numerous possibilities in terms of logistics and handling for an industrial scale-up and transportation of nanomaterials. Overall, stimuli-induced SFFs indeed enable a rapid production of strong, transparent, gas barrier nanopapers, which likely can be industrially scaled up and eventually compete with the oil-based plastics in the market for packaging materials.
纤维素纳米纤维（CNFs）由木质生物质制备，有望替代石油基材料，例如在包装应用中。然而，CNFs 对水的亲和力以及其小尺寸导致在处理和去除水时非常缓慢且耗能。在很大程度上，这是阻止在工业规模上可行地生产基于干燥 CNF 的材料的主要障碍。在这项工作中，通过顺序 TEMPO 和过碘酸盐氧化反应，制备了具有外部刺激可释放纤维的自原纤化纤维（SFF）。然后，使用传统的实验室造纸方法，将这些改性纤维制成纸，然后通过适度的 pH 值增加将其原位纳米原纤化。SFF 的脱水时间不到 10 s，对于 3 g/L 的分散体而言，与传统的 CNF 纳米纸相比，这是一个重大改进，传统的 CNF 纳米纸需要大约 6 h 才能脱水。此外，通过原位原纤化获得的 100 g/m 的纳米纸的性能与通过传统方法制造的 CNF 膜报告的性能相当，如果不是更好的话。SFF 纳米纸的拉伸强度为 184 MPa，杨氏模量为 5.2 GPa，断裂伸长率为 4.6%，透光率为 90%，在 50%相对湿度下的氧气渗透率为 0.7 cm μm m d kPa。此外，SFF 的原位纳米原纤化也可以从已经干燥的纸张中实现，这为工业规模扩大和纳米材料的运输提供了许多物流和处理方面的可能性。总的来说，刺激诱导的 SFF 确实能够快速生产出强韧、透明、气体阻隔性的纳米纸，这可能在工业上具有竞争力，并最终在包装材料市场上与石油基塑料竞争。
