Jiangnan University, School of Chemical and Material Engineering, Wuxi, China.
Perugia University, Civil and Environmental Engineering Department, Materials Engineering Center, UdR INSTM, Terni, Italy.
Int J Biol Macromol. 2020 Oct 15;161:617-626. doi: 10.1016/j.ijbiomac.2020.06.082. Epub 2020 Jun 11.
In the present work, poly(vinyl alcohol) (PVA) active packaging films containing different amounts (1, 3, 5, 10 and 15% wt.) of unmodified cellulose nanocrystals (CNC) and citric acid modified cellulose nanocrystals (mCNC) were prepared by solvent casting and their effect on thermal, mechanical and wettability behaviour of the resulted films was investigated. Results showed that both CNC and mCNC improved the thermal stability of the neat PVA matrix, but different mechanical properties and water wettability were found. Thermal stability of the materials was enhanced, by measuring shift of onset and peak temperatures that moved, respectively, from 251.5 to 298.1 °C and from 283.4 to 374.2 °C, in the case of PVA/15CNC and PVA/15mCNC films. The presence of mCNC contribute to increase the crystallinity up to 52% for PVA/10mCNC film, while it was limited to 39% for PVA/10CNC. Interestingly, PVA/mCNC composite films showed a clear UV shielding effect, while no UV resistance behaviour was detected for PVA/CNC films. Overall migration tests revealed that the migration value was well below the legislative limits (60 mg kg) for food contact materials, PVA/mCNC composite films have higher radical scavenging activity than PVA/CNC films and moisture content of PVA films containing mCNC was reduced at high RH. In conclusion, PVA/mCNC films could be considered as high-performance active food packaging materials.
在本工作中，通过溶剂浇铸法制备了含有不同量（1、3、5、10 和 15wt.%）的未改性纤维素纳米晶（CNC）和柠檬酸改性纤维素纳米晶（mCNC）的聚乙烯醇（PVA）活性包装膜，并研究了它们对所得膜的热性能、力学性能和润湿性的影响。结果表明，CNC 和 mCNC 均提高了纯 PVA 基体的热稳定性，但力学性能和润湿性存在差异。通过测量起始和峰值温度的偏移，可以发现材料的热稳定性得到了增强，分别从 251.5°C 移动到 298.1°C 和从 283.4°C 移动到 374.2°C，这是在 PVA/15CNC 和 PVA/15mCNC 薄膜的情况下。mCNC 的存在有助于将 PVA/10mCNC 薄膜的结晶度提高到 52%，而 PVA/10CNC 薄膜的结晶度则限制在 39%。有趣的是，PVA/mCNC 复合膜表现出明显的紫外屏蔽效果，而 PVA/CNC 膜则没有表现出抗紫外性能。整体迁移试验表明，迁移值远低于食品接触材料的法定限量（60mgkg），PVA/mCNC 复合膜的自由基清除活性高于 PVA/CNC 膜，且高湿度下 PVA 膜中 mCNC 的水分含量降低。总之，PVA/mCNC 膜可以被认为是高性能的活性食品包装材料。
