纤维素纳米晶体对同轴电纺PMMA/PAN复合纳米纤维性能的影响

采用同轴静电纺丝技术,将酸水解获得的纤维素纳米晶体(cellulose nanocrystals,CNCs)添加到聚甲基丙烯酸甲酯(PMMA)/二甲基甲酰胺(DMF)溶液中作为壳层电纺液,聚丙烯腈(PAN)/DMF溶液为核层电纺液,成功制备出核-壳结构的纳米复合纤维。探讨了CNCs添加量对电纺液的电导率和黏度的影响及同轴复合纤维的微观形貌、直径分布、结晶特性、热学性能和疏水性能的影响。结果表明:CNCs添加后电纺液的电导率和黏度有明显提高,所制备的同轴纳米纤维具有较好的核-壳结构,其直径随CNCs加载量的增加而减小,且分布更加集中; 添加高结晶度的CNCs后,复合纤维的结晶性得到明显提高; 在热学性能方面,CNCs增强的同轴纳米材料最大热分解温度为402.7℃,远高于单纺PMMA和单纺PAN纤维以及未添加CNCs的同轴PMMA/PAN纳米材料; 添加亲水性CNCs后,水接触角值由130.0°降低至116.7°,复合纤维的疏水性能明显下降。
A modified coaxial electrospinning process by using poly(methyl methacrylate)(PMMA)solution with different cellulose nanocrystals(CNCs)loadings as sheath fluid and polyacrylonitrile(PAN)solution as core fluid was conducted for preparing composite nanofibrous mats. The CNCs were obtained from α-cellulose via sulfuric acid hydrolysis. The physical properties, including conductivity, viscosity and surface tension, of the as-spin solutions were investigated. The results showed that conductivity of the as-spin solutions increased significantly with the increasing CNCs loading, which was favorite to form uniform fibers. Effects of different CNCs loading on the morphology, crystallinity, thermal behavior as well as hydrophobic properties of the coaxial electrospun PMMA+xCNCs/PAN composite nanofibers were investigated. The transmission electron microscope images of the obtained nanofibrous mats demonstrated that the composite nanofibers with core-shell structure were successfully prepared with the presence of CNCs. Furthermore, the diameters of the composite nanofibers decreased and became more uniform with the increasing CNCs concentration in the shell fluid. The average diameter of the composite nanofibers decreased from 2.09 μm to 1.20 μm. The results from wide angle X-ray diffraction(WAXD)showed that crystallinity increased as a result of the increased loading of CNCs. The thermal stabilities of the CNCs reinforced core-shell nanocomposite mats was much higher than those of the electrospun pure PMMA, PAN, and core-shell PMMA/PAN nanocomposites. The improved thermal stability of PMMA+CNCs/PAN coaxial nanofibrous mats was ascribed to that CNCs could form rigid interconnect network during coaxial electrospinning and form electrostatic attraction effect with PMMA. In addition, the hydrophobicity of the resulting mats decreased when CNCs was incorporated in sheath fluid. The contact angle decreased from 130.0° to 116.7° as the loading of CNCs increased from 0% to 20% due to more hydroxyl groups on CNCs were introduced to the resulting nanocomposite mats. This unique technique to make bio-nanofiller enhanced nanocomposites with