加工芳纶纳米纤维/聚乙烯醇水凝胶制备高强度复合薄膜

芳纶纳米纤维(ANF)具有大长径比、高比表面积、丰富的表面酰胺官能团和优异的力学性能，是制备高强度纳米复合材料的理想构筑单元。本文开发了一种新颖的水凝胶加工策略，用于制备ANF增强聚乙烯醇(PVA)复合薄膜，逐步优化了ANF的含量、水凝胶的预拉伸比和PVA组份的化学交联，表征分析了复合薄膜中ANF的分散、取向、PVA的交联形式及ANF与PVA之间的界面氢键作用，当ANF的质量分数为25wt%、水凝胶的预拉伸比为55%和采用氯化铜交联PVA基体时，复合薄膜的力学性能最优，其杨氏模量和拉伸强度分别高达(14.6±0.3) GPa 和(496.5±10.0) MPa，远远优于文献报道的ANF增强聚合物复合材料。此外，该高强度纳米复合薄膜同时具有良好的透明性和优异的紫外屏蔽性能，透明度大于72.1%，能够屏蔽大于99.98%紫外线，可用做先进包装材料。 

Processing aramid nanofiber/poly(vinyl alcohol) hydrogel into high-strength composite films

Aramid nanofiber (ANF) is an ideal building block for fabricating high-strength composite materials because of its large aspect ratio, high specific area, a plenty of amide group on the surface, and excellent mechanical properties. In this work, a novel hydrogel processing strategy was developed to prepare ANF-reinforced poly(vinyl alcohol) (PVA) composite films. The loading of ANF, pre-stretching ratio of ANF/PVA hydrogel and chemical crosslinking of PVA component were optimized step by step. The dispersion and orientation of ANF, the crosslinking form of PVA, and the interfacial hydrogen bond between ANF and PVA were characterized and analyzed. It is confirmed that the mechanical properties reach maximum values when ANF loading, pre-stretching ratio and the used crosslinking agent are 25wt%, 55% and CuCl₂, respectively. The Young’s modulus and tensile strength of the resultant composite film are as high as (14.6±0.3) GPa and (496.5±10.0) MPa, far superior to previously reported ANF-reinforced polymer composites. Moreover, the high-strength composite film has good transparency and excellent UV light shielding property. Its transmittance is larger than 72.1%, while it can shield more than 99.98% UV light. We believe that the transparent yet UV light-blocking composite film can be applied as advanced packaging materials.