High-strength composite fibers were prepared from polyvinyl alcohol (PVA) (Degree of polymerization: 1500) reinforced by single-walled carbon nanotubes (SWCNTs) containing few defects. The SWCNTs were dispersed in a 10 wt.% PVA/dimethylsulfoxide solution using a mechanical homogenizer that reduced the size of SWCNT aggregations to smaller bundles. The macroscopically homogeneous dispersion was extruded into cold methanol to form fibers by gel spinning followed by a hot-drawing. The tensile strength of the well-oriented composite fibers with 0.3 wt.% SWCNTs was 2.2 GPa which is extremely high value among PVA composite fibers ever reported using a commercial grade PVA. The strength of neat PVA fibers prepared by the same procedure was 1.7 GPa. Structural analysis showed that the PVA component in the composite fibers possessed almost the same structure as that of neat PVA fibers.Hence a small amount of SWCNTs straightforward enhanced by 0.5 GPa the tensile strength of PVA fibers. The results of mechanical properties and Raman spectra for the SWCNT composites suggest the relatively good interfacial adhesion of the nanotubes and PVA that improves the load transfer from the polymer matrix to the reinforcing phase.-3 -

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To exploit the maximum potential of cellulose whiskers (CWs), we report here for the first time the successful fabrication of nanocomposites reinforced with highly oriented CWs in a polymer matrix. The nanocomposites were prepared using polyvinyl alcohol (PVA) and a colloidal suspension of cotton-derived CWs. The macroscopically homogeneous PVA-CW suspensions were extruded into cold methanol to form gel fibers followed by a hot drawing. Compared to the neat PVA fiber, the as-spun fiber containing a small amount of CWs (5 wt % of solid PVA) showed higher drawability, leading to an extremely high orientation of CWs with the matrix PVA. The stress-transfer mechanism, a prime determining factor for high mechanical properties of nanocomposites, was studied by X-ray diffraction. The stress on the incorporated CWs was monitored by applying an in situ nondestructive load to the composite fibers. The applied stress to the whole sample was found to be effectively transferred to the CWs inside the composites, suggesting strong interfacial bonding between the filler and the matrix. Effective stress transfer to the oriented whiskers resulted in outstanding enhancement in mechanical properties of the nanocomposites.

Carbon fibers were fabricated from electrospun poly(vinyl alcohol) (PVA) nanofibers. Electrospun PVA nanofibers were treated with iodine vapor for different periods, subsequently carbonized at different temperatures, and the structural changes of the PVA nanofibers were analyzed. The nanofibers iodinated at 80 C for 24 h led to a good carbon yield of 21% when carbonized at 1200 C. The influence of metal nanoparticle on the fabrication of carbon fiber and its properties was also investigated by the addition of a metal salt, nickel(II) acetate tetrahydrate [(CH 3 COO) 2 Ni:4H 2 O], to the PVA spinning solution. Noticeably, after incorporation of nickel (Ni) nanoparticle continuous electrospinning was realized at lower polymer concentration than that of neat PVA. Moreover, smaller fiber diameter and a higher carbon yield ($34%) were obtained after carbonization. Transmission electron microscopy observation of the carbon fibers revealed that the addition of Ni-nanoparticles accelerated the formation of a graphitic structure at a lower carbonization temperature of 1200 C.

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