The Preparation And Properties Of Graphene Oxide/Cellulose Composites

Nowadays, commercial carbon fibers are mainly manufactured from three kinds of precursor materials, i.e. rayon, polyacrylonitrile (PAN) and pitch. However, with the increasing consumption of fossil oil resources in future, oil based synthetic fiber industries will face great challenges. This will directly result in shortage of raw materials for carbon fibers based on polyacrylonitrile and pitch. As the most abundant and renewable polymer in nature, cellulose is considered to be a promising raw material to replace petrochemically derived compounds to produce carbon fibers. However, the rayon based carbon fibers derived from cellulosic precursors usually have lower mechanical properties because of their disadvantages of low molecular orientation and carbon yield. Therefore, improvement of molecular orientation and carbon yield for the cellulosic precursor are key to improving structure and properties of the resulted carbon fibers. Recently, cellulose carbamate (CC), obtained from cellulose with modification by urea, has presented a promising substitute for traditional viscose process owing to the economical and eco-friendly process and conventional equipment of a viscose plant. Graphene oxide (GO) possesses a planar construction with abundant oxygen-containing functional groups, and can improve the mechanical properties and carbon yields of polymers by interacting with polymers, inducing polymer orientation and enhancing composite interface. So we aim to modify CC using GO to make the precursor of high performance cellulose based carbon fiber.Firstly, mixed GO/CC solutions were prepared by blending, and the rheological properties and stability of the solutions were characterized by dynamic rheology measurements. The CC solution containing2wt.%GO exhibited a decreased viscosity and a wide Newtonian plateau region. Further increasing contents of GO, the complex viscosity rapidly increased especially at low frequency range, and Newtonian regions tended to become narrower, exhibiting the solid-like viscoelastic behavior. Compared to the pure CC solution, all the composite solutions displayed a longer valid spinning time. Moreover, the CC solution with GO loading of2wt.%had the longest valid spinning time, showing a more stable state performance than other GO loadings.Secondly, GO/CC composite films were fabricated by a simple solution-casting procedure. We investigated the effect of GO on the structure and properties of their composite films. X-ray diffraction characterization revealed that GO promoted the transition of crystalline structure of CC from cellulose I to II, and the addition of2wt.%GO improved the orientation and crystallinity of the CC molecules. Scanning electron microscope images indicated that the GO layers were aligned parallel to the surface of the composite films. FT-IR and TEM confirmed that the ways of bonding between GC and CC were both hydrogen bonding and covalent bonding. The incorporation of GO also showed profound effects on the macroscopic properties of the CC film. Compared to the pure CC, the composite film showed a180%increase in tensile strength and280%increase in Young’s modulus by the addition of2wt.%of GO. Moreover, the carbon yields of all the composite films were higher than that of pure CC film.The last but not the least, we carried on wet spinning for the mixed GO/CC solutions, and investigated the effect of GO on the fiber structure and properties of CC by X-ray diffraction and tensile measurements. X-ray diffraction characterization revealed that the addition of1wt.%and2wt.%GO improved the orientation of the CC fiber molecules. The incorporation of GO also showed the enhanced effects on the mechanical properties of CC fiber. Compared to the pure CC fiber, the composite fiber showed a54.2%increase in tensile strength and60.7%increase in Young’s modulus by the addition of2wt.%of GO. These results would provide important information and scientific basis for the fabrication of high orientation and carbon yield of cellulose based carbon fiber precursor, which has important academic value and application prospect.