Investigation On The Preparation And Properties Of Graphene Nanocomposite Fiber By Solution Spinning

Graphene,composed of a monolayer of sp2-hybridized carbon atom in a honeycomb lattice,is a new type of two-dimensional carbon material.It exhibits excellent physical and chemical properties,such as extraordinary mechanical property,remarkable electron mobility and thermal conductivity,large surface area and high thermal stability etc..There are potential applications for graphene in many fields such as energy storage materials,nanocomposite,electronics and photonics.Especially,the large specific surface combined with the unique property make graphene as one of the ideal fillers in polymer nanocomposites,graphene can therefore significantly improve the physical properties of the polymer matrix,such as electrical properties and mechanical properties,and it can also make the nanocomposite material possess new functional properties,such as antibacterial and anti-ultraviolet.The dispersibility of graphene in the matrix,the interaction between graphene and the matrix,and the arrangement of graphene in the matrix are the key factors affecting the performance of graphene/polymer nanocomposites,which is also a hot issue in the areas of the graphene nanocomposite.In this dissertation,focused on the key factors affecting the performance of graphene/polymer nanocomposites,the graphene/polymer nanocomposites fibers with high performance were prepared based on the molecular interaction design and structural design.The main research contents are as follows:1.The graphene oxide(GO)were prepared by the improved two-step Hummers method.After exfoliated the intercalated graphite oxide by the ultrasound treatment,the monodisperse GO with abundant of oxygen functional groups on both the basal plane and edge was obtained,and the thickness of GO is 0.84 nm.Reduced graphene oxide(RGO)was prepared via reducing GO with hydrazine hydrate.The results showed that a large number of oxygen functional groups on GO were removed and some sp2 structures were reconstructed during the reduction process.2.The poly(diallyldimethylammonium chloride)(PDDA)functionalized graphene oxide(FGO)/regenerated silk fibroin(RSF)nanocomposite fiber was prepared by wet spinning.Firstly,the GO was modified by PDDA though electrostatic interaction,the FGO was well dispersed in CaCl2-formic acid solution.Using the FGO /fibroin fibrils mixed solution as the spinning solution,the FGO/RSF nanocomposite fiber was prepared by wet spinning.The effect of FGO on the performance of nanocomposite fiber was investigated.The results showed that FGO was uniformly dispersed in the RSF matrix,and there exists stronger interaction between RSF fibrils and FGO.As a result the stress can be effectively transferred from RSF matrix to FGO,which significantly enhanced the mechanical properties of the nanocomposite fiber.When the FGO content was 0.3 wt.%,the tensile strength of FGO/RSF nanocomposite fiber is 697 MPa,compared with that of the pure RSF fiber,the tensile strength increased by 65.95%,and the mechanical properties of FGO/RSF nanocompsite fiber is superior to natural silk.The FGO/RSF nanocomposite fiber also possess good antibacterial activity aganist E.coli and Staphylococcus aureus.3.The highly aligned GO/poly(vinyl alcohol)(PVA)nanocomposite fiber was prepared by gel spinning,it was found that the GO uniformly dispersed in the matrix and there are strong interaction between the GO with the PVA matrix.The GO exhibited a highly oriention in the parallel direction of the fiber axis,which can greatly enhance the interaction between GO and PVA matrix,and prevent the PVA molecular chain slip more effectively.As a result,the load transfers from the polymer matrix to GO nanosheets efficiently when the nanocomposite fiber is subjected to a tensile force.Compared to pure PVA fiber,the mechanical properties of the GO/PVA nanocomposite fiber was dramatically improved.With only 0.5wt.% GO,the tensile strength increased by 46.15% from 1.3 GPa to 1.9 GPa and the Young's modulus increased from 26 GPa to 31.2 GPa.However,when the addition of the GO nanosheets is larger than 0.5 wt.%,the tensile strength of the resulting nanocomposite fiber decreased with the increase of GO content.This is probably because the GO nanosheets tend to aggregate when GO addition increased above a critical point.The GO/PVA nanocomposite fiber exhibited excellent UV-blocking property,the ultraviolet protection factor(UPF)value of the 0.3 wt.%GO/PVA nanocomposite fiber was 306,16-fold higher than that of neat PVA fiber(UPF 18.5).The GO/PVA nanocomposite fiber also exhibited good antibacterial activity aganist E.coli and Staphylococcus aureus.