Reinforcement of poly (vinyl alcohol) films with alpha-chitin nanowhiskers

Abstract Composites Films were produced using Poly (Vinyl Alcohol) as the soft material and reinforced with Chitin Nanowhiskers(NWCH) as the rigid material. The present work studies the reinforcing mechanisms of NWCH in PVA films, made through a solvent casting technique and characterized for their calorimetric, swelling and mechanical properties. DSC tests revealed a sharp increase of 45 °C in glass transition temperatures with only 1.5% NWCH, while melting temperature had a small increases suggesting an anti-plasticizing effect. Swelling tests revealed decreasing hygoscopy when NWCH volume fraction increases. Estimates for elastic tensile modulus using a model that predicts the formation of a percolating network were not consistent with the experimental data of tensile tests suggesting that contrary to the reinforcement with cellulose nanowhiskers the percolating network is not primarily responsible for the reinforcement of the films. By adjusting the Halpin-Tsai equations, modified by Nielsen it was found that the mechanical properties were mainly influenced by the packing of the NWCH.

摘要 本研究以聚乙烯醇（Poly (Vinyl Alcohol)）作为软质基体材料，以甲壳素纳米晶须（Chitin Nanowhiskers, NWCH）作为刚性增强相制备复合薄膜。本研究旨在探究NWCH在该溶剂浇铸法制备的PVA复合薄膜中的增强机制，并对其热学性能、溶胀性能与力学性能进行表征。差示扫描量热法（DSC）测试结果显示，仅添加1.5%的NWCH即可使复合薄膜的玻璃化转变温度升高45℃，而熔融温度仅出现小幅提升，表明NWCH对基体具有抗塑化效应。溶胀测试结果表明，随着NWCH体积分数的增加，复合薄膜的吸湿性逐渐降低。采用预测渗滤网络形成的模型对弹性拉伸模量进行估算，所得结果与拉伸试验的实验数据并不一致，这表明与纤维素纳米晶须增强体系不同，渗滤网络并非该复合薄膜增强效应的主要来源。通过调整经Nielsen修正的Halpin-Tsai方程开展分析后发现，NWCH的堆积状态是影响复合薄膜力学性能的核心因素。