Characterization of UHMWPE Nanocomposite Fibers Reinforced with PVP-coated SWCNTs

Ultra-high molecular weight polyethylene (UHMWPE) fibers were fabricated using solution spinning, consisting of surface modified SWCNTs embedded into the fiber matrix. The CNTs were modified using a physical functionalization process to enhance their dispersion in the UHMWPE fiber matrix. The physical functionalization was performed using Polyvinylpyrrolidone (PVP), which acts as a surfactant due to its ability to be physically adsorbed or grafted onto the surface of CNTs. The physical adsorption of PVP on CNT surfaces is significantly enhanced by ultrasonic processing. Furthermore, sufficient modification of the CNT surface with a surfactant polymer layer can enable their enhanced interfacial adhesion with the base polymer matrix and also reducing their agglomeration. The purpose is to compare the effect of adding functionalized vs. non-functionalized SWCNTs in a fiber matrix, by analyzing the physical, chemical, and mechanical properties. Morphological characterization of modified nanotubes and produced fibers were performed using Scanning Electron Microscopy (SEM). SEM micrographs of the modified CNTs showed an increase in average tube diameter compared to pristine CNTs. The diameter increase can be attributed to the successful coating of PVP. SEM images of the hybrid UHMWPE fibers (with PVP-coated CNTs) indicated the presence of CNTs aligned along the direction of the extrusion on the fiber. Thermogravimetric analysis (TGA) was performed to estimate the amount of grafted PVP content on the CNT surfaces after the functionalization process. The TGA results showed an approximate PVP grafting percentage of ~21.4%. Differential scanning calorimetry (DSC) was used to compare the crystallinity of both the neat and hybrid fibers. The DSC results showed an increase in crystallinity of the fibers with the inclusion of PVP modified CNTs when compared to neat UHMWPE. Further characterization includes Fourier transform infrared spectroscopy (FTIR), in order to analyze the nature of bonding between the CNTs and the polymer phases. Thermal conductivity of the surface modified CNTs will be measured and compared to that of pure PVP and pristine CNTs