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)）作为柔性基体材料，以甲壳素纳米晶须（Chitin Nanowhiskers, NWCH）为刚性增强相制备复合薄膜。本工作针对通过溶剂浇铸法（solvent casting technique）制备的PVA复合薄膜，探究了NWCH的增强机理，并对其开展量热、溶胀及力学性能表征。差示扫描量热法（DSC）测试结果显示，仅添加1.5%的NWCH即可使薄膜的玻璃化转变温度升高45℃，而熔融温度仅小幅上升，表明NWCH对该复合薄膜具有抗塑化效应。溶胀测试结果表明，随着NWCH体积分数的提升，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测数据并不一致，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。通过调整经尼尔森（Nielsen）修正的哈尔平-蔡（Halpin-Tsai）方程后发现，复合薄膜的力学性能主要受NWCH的堆积状态影响。