Study On Fiber-foriming And Fiber Structure Of GO/PAN Solution

Graphene fiber has attracted much attention as an important one-dimensional graphene material for macroscopic assembly.Its essence is to arrange graphene sheets regularly along the fiber axis direction.Thus,the excellent optical,mechanical,electrical,thermal and other properties of graphene are converted into macroscopic properties.At present,graphene fiber not only has many holes and defects,but also lacks the chemical bond between graphene sheets,which cannot perform well the excellent performance of graphene.The pre-oxidation and carbonization process of polyacrylonitrile(PAN)is similar to the thermal reduction process of graphene oxide(GO),and all of them are converted into a graphite structure by subsequent heat treatment,which has certain electrical and thermal conductivity.Therefore,this paper intends to combine graphene oxide with a small amount of polyacrylonitrile to prepare fibers by wet spinning,and to study on fiber-forming and fiber structure of graphene/polyacrylonitrile solution,which will provide theoretical guidance for the preparation of the precursors of graphene fibers with excellent structure.The existence form,functional group structure and interaction of GO solution and PAN solution were studied by means of transmission electron microscopy(TEM),scanning electron microscopy(SEM),polarized optical microscopy,Fourier transform infrared spectroscopy(FTIR),ultraviolet spectroscopy(UV),rotary rheometer,X-ray photoelectron spectroscopy(XPS).The effects of coagulation bath composition,composition ratio of coagulation bath and PAN content on the structure of GO/PAN fibers prepared by wet spinning were studied by means of optical microscopy,scanning electron microscopy(SEM),X-ray diffraction(XRD),Raman spectroscopy(Raman),and rotary rheometer.The results showed that:1.The GO solution exists in the form of a uniformly ordered layered nematic liquid crystal.However,the GO/PAN mixed solution still exists nematic liquid crystal after adding a small amount of PAN solution.Moreover,the PAN molecule has a weak interaction with the oxygen-containing functional group of GO.The section of the GO/PAN fiber is dense,and the GO sheets in the fibers are layered in a direction parallel to the fiber axis.2.The coagulation bath component affects the fiber formation of the GO/PAN solution.When the coagulation bath system contains the solvent DMF,it is beneficial to the double diffusion of the solvent in the GO/PAN solution and the coagulant in the coagulation bath through on the surface of the fiber.SEM electron microscopy studies show that when the coagulation bath component is composed of ethanol/H2O/DMF,the diameter of GO/PAN fibers is more uniform and finer,and the surface structure is more regular.3.In the three-component coagulation bath system with ethanol/H2O/DMF,as the concentration of ethanol in the solution decreases,the DMF concentration increases,diameter of the fiber gradually decreases,the groove surface of the fiber surface is more uniform and has a distinct orientation along the fiber axis direction.The disorder degree of GO layer in GO/PAN fiber gradually decreases,and the layer spacing of GO sheet gradually decreases.It is indicated that the composition and concentration of the coagulation bath affect the alignment of GO layer and PAN molecular chain.4.In the GO/PAN solution system,as the content of PAN increases,the difference in brightness and darkness of the polarized microscopic image of the GO/PAN solution decreases.With the increase of PAN content,the storage modulus,loss modulus and complex viscosity of GO/PAN solution increase gradually,while the mechanical loss angle increases and then decreases.When the PAN content is about 28.6%,the PAN content adhered to the GO sheet layer is the most.5.In the GO/PAN composite fiber,X-ray diffraction studies show that as the PAN content increases,the crystallinity and the grain size of PAN in GO/PAN fiber increases gradually,and the GO layer spacing increases gradually.Raman spectroscopy studies show that the half-peak width increases gradually with the increase of PAN content,which means that the disorder of GO layer increases.