Pretreatment Of Graphene And Preparation Of Its Composite Fiber With Poly (vinyl Alcohol)

Due to the excellent properties of graphene, the preparation of polymer nanocomposites have become a hot research topic in recent year. The composite fiber of poly（vinyl alcohol） and graphene with pretreatment was prepared and the structure and properties of the composite fiber were studied. On the one hand, by putting reduced graphene oxide（rGO） with high strength and high modulus into poly（vinyl alcohol）（PVA） matrix, PVA/rGO composite fibers with enhanced mechanical properties can be prepared. On the other hand, large graphene oxide suspension with narrow distribution and high concentration was prepared through pretreatment. And then by using a small amount of PVA as the ‘binder’ of graphene nanosheets, the interaction between graphene sheets can be significantly strengthened. On this basis, the prepared graphene fiber can possess obviously improved mechanical properties and at the same time maintain the flexibility of PVA.The main research details and conclusions are as follows:（1） The graphene oxide（GO） was prepared by Hummers’ method, and was reduced by oligomeric proanthocyanidin（OPC）. The reduction effect, the surface adsorption state and the dispersibility of rGO were characterized. The results show that most of oxygencontaining groups of GO can be removed by OPC. At the same time, some OPC molecules that combined with rGO sheets can serve as the dispersant of rGO and improve the dispersibility of rGO in solvents.（2） Continuous PVA/rGO composite fibers with different rGO loadings were prepared by wet spinning followed by hot drawing, and the surface morphology, crystalline properties and mechanical properties of the composite fibers were studied. The results show that there is a strong interfacial interaction between rGO and PVA matrix. In addition, the dynamic mechanical properties and tensile properties of the composite fibers exhibit a trend of first increasing and then decreasing with the increasing of rGO loading. And when rGO loading reaches 2.0 wt%, the optimum reinforcement is achieved.（3） Through improved oxidation and separation methods, we successfully prepared large graphene oxide（LGO） suspension with narrow distribution and high concentrations. The viscosity of graphene suspension and the morphology under polarized optical microscopy（POM） were characterized after PVA was added into the suspension and cross-linked with boric acid. The results show that the addition of PVA and boric acid could greatly increases the viscosity of the suspension, and the final suspension shows liquid crystal morphology.（4） With NaOH/CH₃ OH solution as the coagulation both, the LGO suspension with PVA and boric acid was wet-spun to prepare graphene fiber followed by shrunk in methanol and reduced by hydrogen iodate. The morphology and the mechanical property of the graphene fiber was characterized. The results show that the interaction between graphene sheets and the spinnability of the suspension can be increased by adding of PVA and boric acid. The shrinking treatment in methanol can make the graphene fiber become tight and obtain a relatively regular cross section. What’s more, the graphene fiber has a significantly improved mechanical property.