Lundahl Meri J, Cunha A Gisela, Rojo Ester, Papageorgiou Anastassios C, Rautkari Lauri, Arboleda Julio C, Rojas Orlando J
Aalto University, Department of Forest Products Technology. P.O. Box 16300, 00076 Aalto, Finland.
Turku Centre for Biotechnology, University of Turku and Åbo Akademi University, 20520 Turku, Finland.
Sci Rep. 2016 Jul 28;6:30695. doi: 10.1038/srep30695.
Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as determined by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young's modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, respectively, which are remarkable values. A thorough investigation of the interactions with water using dynamic vapour sorption (DVS) experiments revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS analysis during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge density (CNF and TEMPO-oxidised CNF). It is concluded that the mechanical performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the maximum water vapour sorption at 95% RH was 39% based on dry weight.
包含纤维素纳米原纤维（CNF）的水凝胶通过湿法纺丝用于连续长丝的合成。发现水凝胶粘度和可纺性以及纺丝长丝的取向和强度受到由纺丝原液中CNF表面电荷和固体分数所确定的渗透压的强烈影响。未拉伸生产的长丝的拉伸强度、杨氏模量和取向度（广角X射线散射，WAXS）分别为297MPa、21GPa和83%，这些都是显著的值。使用动态蒸汽吸附（DVS）实验对与水的相互作用进行的深入研究揭示了吸附位点在潮湿条件下长丝稳定性中的作用。在0至95%的相对湿度（RH）循环期间的DVS分析揭示了从不同电荷密度（CNF和TEMPO氧化的CNF）的水凝胶纺出的长丝在吸水方面的主要差异。得出的结论是，促进原纤维排列并因此提高干强度的相同因素会使有水存在时长丝的机械性能急剧下降。对于取向度最高的长丝，在95%RH下的最大水蒸气吸附量基于干重为39%。
