Guo Xin, Wu Yiqiang, Xie Xinfeng
College of Material Science and Engineering, Central South University of Forestry and Technology, Changsha, 410004, China.
School of Forest Resources and Environmental Science, Michigan Technological University, Michigan, 49931, United States.
Sci Rep. 2017 Oct 27;7(1):14207. doi: 10.1038/s41598-017-14664-7.
Hygroscopic behavior is an inherent characteristic of nanocellulose which strongly affects its applications. In this study, the water vapor sorption behavior of four nanocellulose samples, such as cellulose nanocrystals and nanofibers with cellulose I and II structures (cellulose nanocrystals (CNC) I, CNC II, cellulose nanofibers (CNF) I, and CNF II) were studied by dynamic vapor sorption. The highly reproducible data including the running time, real-time sample mass, target relative humidity (RH), actual RH, and isotherm temperature were recorded during the sorption process. In analyzing these data, significant differences in the total running time, equilibrium moisture content, sorption hysteresis and sorption kinetics between these four nanocellulose samples were confirmed. It was important to note that CNC I, CNC II, CNF I, and CNF II had equilibrium moisture contents of 21.4, 28.6, 33.2, and 38.9%, respectively, at a RH of 95%. Then, the sorption kinetics behavior was accurately described by using the parallel exponential kinetics (PEK) model. Furthermore, the Kelvin-Voigt model was introduced to interpret the PEK behavior and calculate the modulus of these four nanocellulose samples.
吸湿行为是纳米纤维素的固有特性，这对其应用有很大影响。在本研究中，通过动态蒸汽吸附研究了四种纳米纤维素样品（如具有纤维素I和II结构的纤维素纳米晶体和纳米纤维，即纤维素纳米晶体（CNC）I、CNC II、纤维素纳米纤维（CNF）I和CNF II）的水蒸气吸附行为。在吸附过程中记录了包括运行时间、实时样品质量、目标相对湿度（RH）、实际RH和等温温度在内的高度可重复的数据。在分析这些数据时，证实了这四种纳米纤维素样品在总运行时间、平衡水分含量、吸附滞后和吸附动力学方面存在显著差异。需要注意的是，在95%的相对湿度下，CNC I、CNC II、CNF I和CNF II的平衡水分含量分别为21.4%、28.6%、33.2%和38.9%。然后，使用平行指数动力学（PEK）模型准确描述了吸附动力学行为。此外，引入了开尔文-沃伊特模型来解释PEK行为并计算这四种纳米纤维素样品的模量。
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