ABSTRACT:In this study, we propose a novel method for preparing a continuous filament using electrospinning and twisting methods to improve the mechanical properties of nonwoven poly(vinylidene fluoride) (PVDF) nanofibers. The morphologies of the nonwoven nanofiber membranes and the corresponding nanofiber filaments were investigated by scanning electron microscopy. The mechanical properties and crystal structure of both the nanofiber membranes and the nanofiber filaments were investigated by using a universal testing machine and wide-angle X-ray diffraction (WAXD), respectively. We found that the tensile strength and Young's modulus of nanofiber filaments were dramatically improved by increasing either the number of twists of the nanofibers or the width of nanofiber membranes, compared with nonwoven PVDF nanofibers. WAXD analysis indicated that the crystalline transformation from β-phase to α-phase occurred by the shear force driven by repeated twisting. It was concluded that

Herein, we report a new Prussian blue nanoparticle (PBNPs) incorporated polyvinyl alcohol (PVA) composite nanofiber (c-PBNPs/PVA) for a rapid adsorption of cesium (Cs) from the radioactive 10 wastewater. Initially, various electrospinning parameters such as solvent, PVA wt%, PBNPs wt% and glutaraldehyde (GA) wt% were extensively optimized to obtain a better physicochemical property of the c-PBNPs/PVA. In order to improve the water insoluble nature of the PVA, a post cross-linking was carried out for the c-PBNPs/PVA using glutaraldehyde (GA) and HCl vapor as cross-linker and catalyst, respectively. SEM images revealed smooth and continuous morphology of the c-PBNPs/PVA composite 15 nanofibers with diameters of 200-300 nm and lengths up to several millimeters. TEM images confirmed homogeneous dispersion and well incorporation of PBNPs into PVA matrix. The amorphous nature of the c-PBNPs/PVA was confirmed by the XRD analysis. FT-IR spectra showed successful cross-linking of PVA with GA. It was found that the prepared composite nanofiber is highly hydrophilic and waterinsoluble. The c-PBNPs/PVA showed an excellent and faster Cs adsorption rate of 96 % after only 100 20 min. These results are well comparable to those previous reported. After the Cs adsorption test, the cPBNPs/PVA composite nanofiber can be easily separated from the wastewater.

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In the present work, we conducted the frictional tests of hydrophobic and hydrophilic polyurethane (PUo and PUi) nanofiber webs against engineering materials; soda-lime glass and silicon wafer. PUi/glass combination, with highest hydrophilicity, showed the highest friction coefficient which decrease with the increase of the applied load. Furthermore, the effects of fluorine coating are also investigated. The friction coefficient of fluorine coated hydrophobic PU nanofiber (PUof) shows great decrease against the silicon wafer. Finally, wiping ability and friction property are investigated when the substrate surface is contaminated. Nano-particle dusts are effectively collected into the pores by wiping with PUo and PUi nanofiber webs both on glass and silicon wafer. The friction coefficient gradually increased with the increase of the applied load.