Self-assembled optically transparent cellulose nanofibril films: effect of nanofibril morphology and drying procedure
Self-assembled optically transparent cellulose nanofibril films: effect of nanofibril morphology and drying procedure
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DOI：
10.1007/s10570-015-0563-9
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发表时间：
2015-02
期刊：
影响因子：
5.7
通讯作者：
Yan Qing;R. Sabo;Yiqiang Wu;J. Y. Zhu;Z. Cai
中科院分区：
文献类型：
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作者：
Yan Qing;R. Sabo;Yiqiang Wu;J. Y. Zhu;Z. Cai
纤维素纳米原纤维（CNF）膜目前在许多应用中提供了巨大的机会，其具有优异的机械强度、高透光率和良好的阻隔性能的优点。然而，用于制备CNF的方法通常是冗长的并且随着它们的性质沿着变化。在这里，使用过滤，冷冻干燥和铸造的各种组合的五种制备方法被应用于生产CNF膜，并比较它们的主要性能。使用这五种制备方法中的每一种来检查具有一定范围的纤维直径和纵横比的三种不同类型的CNF。由于有限的氢键和纳米纤维排列，冷冻干燥的CNF膜显示出降低的机械强度和透光率相比，其他方法，虽然冷冻干燥是相对较快的。还观察到膜生产方法对测量结晶度的一些影响，其中冷冻干燥的样品具有比通过过滤和干燥类似地生产的膜更低的结晶度。通过在室温下流延制备的自支撑CNF膜需要很长时间，有时会观察到霉菌生长，但由2，2，6，6-四甲基哌啶-1-氧自由基氧化的CNF制成的流延膜具有所有样品中最高的透光率。过滤CNF悬浮液，然后进行空气干燥或烘箱干燥，以相对较少的努力产生具有最小缺陷、高机械强度和良好透光率的膜。因此，推荐该过滤程序用于生产CNF膜。
Cellulose nanofibril (CNF) films currently provide great opportunity in many applications with advantages of excellent mechanical strength, high light transmittance, and good barrier properties. However, processes for preparing CNFs are typically tedious and vary, along with their properties. Here, five preparation methods using various combinations of filtration, freeze-drying, and casting are applied to produce CNF films, and their major properties are compared. Three different types of CNFs having a range of fiber diameter and aspect ratio were examined using each of these five preparation methods. Because of limited hydrogen bonds and nanofibril arrangement, the freeze-dried CNF films displayed reduced mechanical strength and light transmittance compared to the other methods, although freeze-drying was relatively fast. Some effects of film production methods on measured crystallinity were also observed with freeze-dried samples having lower crystallinity than films similarly produced by filtration and drying. Free-standing CNF films produced by casting at room temperature required long times and mold growth was sometimes observed, but cast films made from 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized CNFs had the highest light transmittance of any samples. Filtration of CNF suspensions followed by air- or oven-drying produced films with minimal defects, high mechanical strength, and good light transmittance with relatively little effort. Therefore, this filtration procedure is recommended for producing CNF films.