聚乙烯醇/纳米纤维素/石墨烯复合薄膜的制备与性能

利用生物质纳米纤维素纤维的高强度和高长径比,向聚乙烯醇中引入纳米纤维素,可改善薄膜的拉伸性能。针对聚乙烯醇阻隔性能的改善问题,选用片层的还原氧化石墨烯作为增强相,将自制的纳米纤维素和氧化石墨烯加入聚乙烯醇溶液中,以D-果糖为绿色还原剂,分别添加质量分数0.2%,0.4%,0.6%,0.8%的还原氧化石墨烯,采用浇涂法制备聚乙烯醇/纳米纤维素/石墨烯复合薄膜。通过纳米纤维素与石墨烯的协同增强作用,研制了兼具优良阻隔性能和拉伸性能的生物降解薄膜。结果表明,当纳米纤维素和石墨烯质量分数分别为0.8%和0.6%时,聚乙烯醇/纳米纤维素/石墨烯复合薄膜的拉伸强度、氧气透过系数、对水的接触角和吸水率分别为88.76 MPa、0.592×10-15cm3？cm/(cm2？s？Pa)、90.5°和72.9%。但石墨烯的用量存在一个阈值,当质量分数高于0.6%时,复合薄膜的力学和阻隔性能反而下降。
As a biodegradable polymer, polyvinyl alcohol(PVA)has advantages of good water solubility, excellent film forming property and adhesive capability, being widely used in packaging applications. However, its application is severely limited by the low mechanical strength and poor barrier properties. Nanomaterials, such as cellulose nano fiber(CNF), graphene oxide(GO), etc., have been introduced into polyvinyl alcohol substrate. Since the biomass nano-cellulose fibers have high strength and high aspect ratio, introducing nano-cellulose into polyvinyl alcohol can improve the tensile properties of the films. At the same time, the sheet structure of reduced graphene oxide(rGO)can expand the barrier path, so that the barrier properties also can be improved. In this paper, the GO was firstly prepared by the modified Hummers method from graphite powder and the CNF was extracted from bamboo powder by the acid-alkali alternate treatments combined with mechanical grindings method. Secondly, the GO was reduced into the rGO in situ using D-fructose as a green reducing agent. Then, PVA/CNF/rGO films were prepared with a simple casting method. A new type of biodegradable PVA based film with excellent tensile and barrier properties was developed through the synergistic enhancement of CNF and rGO. At last, the obtained PVA/CNF/rGO films were characterized and analyzed by the FT-IR, Raman, SEM, tensile property, barrier property, etc. The results were summarized as follows. The FT-IR examination indicated that the hydrogen bonding existed between the interface of rGO and PVA-CNF. The scanning electron microscopy results showed that rGO was uniformly dispersed in PVA-CNF matrix. Introducing CNF into PVA caused a significant improvement in tensile strength, and further incorporating rGO into PVA/CNF matrix led to a further increase. The tensile strength of the neat PVA film, PVA/CNF composite, and PVA/CNF/rGO film(0.6 wt% rGO)were 43.15 MPa, 69.19 MPa, and 88.76 MPa, respectively. Moreover, when incorporating 0.8 wt% CNF into PVA matrix, the oxygen permeability coefficient and water absorption decreased from 2.31×10-15 to 2.13×10-15 cm3？cm/(cm2？s？Pa), and from 164.2% to 98.8%,