Dispersion Of MWCNTs And Preparation Of PVA/MWCNTs Composite Fibers

Effective methods were studied to increase the dispersion of multi-walled carbon nanotubes(MWCNTs) via modifying them in physical and chemical ways in this paper. The modified MWCNTs were then blended with poly(vinyl alcohol)(PVA) as fillers to prepare composite fibers through wet spinning and hot drawing process. The main contents and conclusions are as follows:(1) Functionalized MWCNTs(f-MWCNTs) were prepared through grafting PVA to MWCNTs surface by Friedel-Crafts alkylation and the reaction conditions were optimized. 13 C NMR and Raman spectra have proved that the chemical bonding between PVA and MWCNTs existed. The dispersion of f-MWCNTs in the solvent(DMSO/H2O(vol ratio= 3/1)) was characterized byTecnaiG220 transmission electron microscopy(TEM) and Ultraviolet-visible(UV-vis). The results indicated that the structural of carboxyl group traditionally acid-treated MWCNTs(c-MWCNTs)was destructive damaged, while f-MWCNTs are homogeneously dispersed in the solution and show no obvious destructive structural damage on the surface.(2)The f-MWCNTs with best dispersion properties were selected as fillers for PVA and the composite solution was wet spun to prepare PVA/ f-MWCNTs composite fibers. The as spun fibers were then hot drawn with different ratio. The mechanical, morphological, thermal and electrical properties of the composite fibers were studied. The maximum tensile strength and modulus of the fibers were found to be about 926 MPa and 59 GPa, which increased by 280.6% and 421.0% compared to pure PVA fibers, respectively. However, the PVA/c-MWCNTs composite fibers showed poor mechanical properties. Thermal gravimetric analysis(TG) showed that thermal stability of the composite fibers contains f-MWCNTs was much better than those containing the c-MWCNTs. Differential scanning calorimetric(DSC)curves indicated that well dispersed MWCNTs could hinder the crystallization of PVA. Scanning electron microscopy(SEM) images illustrated that the introduction of f-MWCNTs could strengthen the interactions between MWCNTs and PVA matrix. When f-MWCNTs content is up to a certain value, the f-MWCNTs began to aggregate which will badly impair the mechanical and electrical properties.(3) To be contrast with the chemical modification of MWCNTs, physically modified MWCNTs(m-MWCNTs) were prepared using rosemary acid(RosA) as surfactant to achieve good dispersion in aqueous media. UV-vis curves showed that the m-MWCNTs dispersion can keep stable for 30 days at room temperature. TEM images displayed that the regular graphite structure of the m-MWCNTs was not destructed after the modification.1H NMR and Raman spectra demonstrated that the ??? stacking existed between RosA and MWCNTs.(4) The m-MWCNTs and PVA solution were blended, and then the blended solution was wet spun and hot drawn to obtain PVA/m-MWCNTs composite fibers. The thermal properties of the fibers were studied by DSC and the results indicated that as a nucleating agent in the PVA/m-MWCNTs system, the m-MWCNTs facilitated the crystallization of PVA during the cooling process. In addition, the m-MWCNTs greatly improved the tensile strengths and Young’s modulus.