The purpose of this study is to make use of the advantages of both polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) to fabricate a flexible electronic device. polyvinylidene fluoride (PVDF)/polyacrylonitrile (PAN) composite fibrous mats with different blend ratios were fabricated using electrospinning. The effects of PVDF and PAN mass ratio on fiber morphology, chemical structure, thermal stability, and piezoelectric properties of the produced composite fibers were investigated by scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), and piezoelectric tester. The SEM images showed that the PVDF/PAN composite nanofibers were fabricated successfully and fiber diameters increased with the increase of PVDF content. The FTIR and XRD analyses showed that both the α,-and β,-crystal phases existed in PVDF/PAN composite fibers. The thermal stability of PVDF/PAN fibrous mats was less than that of neat PVDF fibers. The piezoelectric properties of PVDF/PAN fibrous mats were significant and a function of PVDF content. The output voltage of PVDF/PAN fibrous mats increased from 1. 2 to 5. 0 V as PVDF content increased from 20 to 100%. The piezoelectric voltages of PVDF/PAN composite nanofibers also increased with the increase of impacting force. Tensile and contact angle testing indicated that the PVDF/PAN fibrous mats were more flexible and hydrophilic than neat PVDF membrane. PVDF/PAN nanocomposite fiber mats were observed suitable for potential application in flexible electronic devices.

Background: Recently, concerns have been raised regarding the environmental and public health safety of azo dyes, the most widely used synthetic dyes. The membrane technique has been introduced as one of the efficient methods for dye removal treatments. polyvinylidene fluoride (PVDF) membrane manipulated by surfactants was studied for removal of the azo dye, carmoisine. Methods: PVDF membrane was prepared via non-solvent-induced phase separation (NIPS) and used to remove the azo dye, carmoisine. Three nonionic surfactants including Tween 20, Tween 60, and Tween 80 were used individually as additives in casting solutions to improve PVDF membrane properties. Results: Fourier-transform infrared spectroscopy (FTIR) demonstrated the presence of functional groups of carbonyl (C=O) and hydroxyl (OH), assigned to Tween molecules, in the membrane chemical structure. All Tween species caused a decrease in the surface hydrophobicity of PVDF membranes illustrated by the reduced contact angles. Each Tween at a 2% concentration in the dope solution led to an increase in the pore-size of PVDF membranes, which was estimated by scanning electron microscopy (SEM). However, this impact was reversed at Tween concentrations of 4%. Membranes were assessed for dye removal efficiency and permeate flux in a cross-flow system. Permeability of PVDF membranes improved (~78%) with adding Tween 80 at a concentration of 2%. Tween 60 at a 2% concentration resulted in a ~45% increase in dye removal efficiency of PVDF membranes. And, atomic force microscopy (AFM) showed that Tween 60 increased membrane surface roughness. Conclusion: Surfactant-mediated changes in the surface properties of PVDF membrane improved dye removal efficacy.

In this work the coexistence effect of Cloisite 30B and multi-walled carbon nanotubes (MWCNT) on the crystal transformation of the polyvinylidene fluoride (PVDF) matrix is reported. It was found that at a constant rate of 3% (by weight) total modification, a higher percentage of beta crystal was evolved in PVDF matrix as compared with that of 3% (by weight) of each nanomaterial in the whole nanocomposite system. These changes in the crystalline structure were quantitatively and qualitatively studied using FTIR and WXRD techniques, respectively. The FTIR technique confirmed the formation of 80%, 71% and 84% of beta crystal for the three prepared composites. The small-angle X-ray scattering (SAXS) technique revealed a 10-time increase in the d-spacing of the nanoclay in nanocomposites as compared with that in raw nanocaly.The morphology of the nanomaterials and the state of dispersion were investigated using SEM and TEM techniques. The synergism observed was assigned to differences in surface conformations and aspect ratio of the nanomaterials. These nanocomposites ensured formation of beta crystals without any need to apply strain. Meanwhile, the piezoelectric constant (d33) of the hot-pressed samples was found to be zero. To attain piezopyroelectric characteristics, there was a need to cold-drawing, probably by smaller strain which resulted in better mechanical properties and anisotropy of the resulting hybrid nanocomposite.

The changes in the crystalline structure of polyvinylidene fluoride (PVDF) were investigated via preparation of its blends with polymethyl methacrylate (PMMA), polyethylene terephthalate (PET) and polyvinyl chloride (PVC) in molten states in an internal mixer at 10% to 40 wt% of the last two polymers. In all the blends, an increase in b-crystal content of PVDF was observed at different degrees and different morphologies. polyvinylidene fluoride blends with PMMA showed a homogeneous morphology, whereas those with PET and PVC showed two-phase morphologies. These were accounted for the solubility parameter differences of the polymers. In the case of PVC the mismatch of processing conditions was found to be the main reason for the observed morphology. The technique of FTIR spectroscopy revealed that the relative b-crystal content of PMMA blend reached 70% at 30 wt% PMMA, whereas PET and PVC achieved 80% b-crystals by only 10 wt% modification. This was attributed to the interactions of the blended polymers with PVDF molecules in amorphous regions or at their interphases. The effects of PVC and PET on the beta-crystal content of PVDF are similar although the blends in the case of PET produce finer morphology as compared with those of PVC. It is desirable to find and maximize the content of PVDF in final piezoelectric article. The technique of WXRD shows limited changes in shape and position of PVDF/PMMA and PVDF/PVC blends spectra and considerable changes in shape of PVDF/PET blends spectra. This is found to be related to the amorphous and semi-crystalline structures of PVC and PET, respectively. Due to the spherical symmetry of the PVDF spherulites the piezoelectric coefficient of the blends are found to be zero.

polyvinylidene fluoride (PVDF) is one of the well-known polymers in different types of ‎membranes for water treatment applications, because of its unique chemical, mechanical and ‎thermal properties. Because of the presence of fluorine groups in polymer chain, the PVDF has ‎a negative electrostatic surface charge that makes the PVDF a suitable adsorbing material for ‎cationic dyes such as Rhodamine B (RB) and Methylene Blue (MB). The presence of two-‎dimensional graphene oxide sheets with negative electrostatic surface charge in the PVDF ‎matrix, can improve the adsorption of the dyes on PVDF/graphene oxide (PGO) composite ‎membranes due to increasing of negative electrostatic charge. In this study, we aimed to ‎explore synthesis and characterization of the PGO composite membranes by Scanning Electron ‎Microscopy (SEM), Atomic Force Microscopy (AFM), Raman spectroscopy, X-Ray diffraction ‎‎(XRD), to confirm the effective presence of the GO sheets in PVDF matrix. In continue, the ‎mechanisms of physical adsorption of the dyes on PGO membranes have been investigated‎‎.

Current research, has evaluated the efficiency of the membrane process in degumming and neutralization of crude rapeseed oil. Crude rapeseed oil miscellas were prepared using hexane solvent with 20:80 and 30:70 ratios. In order to degumming, the micella passed through the membrane   after adding 0.3% of 85% (w/w) phosphoric acid, under three pressure levels of 2, 3, and 4bar and two flow speed of 0.5 and 1m/s; Then, for neutralization, after adding NaOH aqueous solution in two concentrations of 10% and 30% (w/v) the micella passed through the membrane, under the previous conditions, as well as three temperature levels of 30, 40 and 500C. The results showed that for 20:80 micella, the flux gradually decreased with the passage of time and reached a stable state after about 20 minutes. Surveying the simultaneous effect of conditions throught the neutralization process for 20:80 micella, revealed that the highest flux corresponds to 400C, 4bar, 1.0m/s. Surveying the simultaneous effect of temperature, pressure and flow rate throught the neutralization process for 30:70 micella, has also revealed that the highest flux corresponds to 500C, 2bar, and 1.0m/s. The results of the physicochemical tests also revealed that there is no significant difference in the levels of phosphorus and phosphates in both membrane filtration and conventional rifining methods (p<0.01); But acidity reduction for membrane filtration method was significantly higher than that of classical refining method (p<0.01). The reduction of peroxide index was also significantly higher for classic refining method than membrane filtration method (p<0.01). In terms of color, the results showed that the membrane filtration method was not able to reduce the yellow color in crude oil, while the classic refining method significantly reduced the yellow color (p<0.01). The red color index for the classic method also had a significant decrease compared to the membrane method (p<0.01).

Background: The limited availability of donor sites for nerve grafting has continued to stimulate research toward finding suitable alternatives for autograft. The aim of this research was to study the effect of piezoelectric channel and collagen gel on nerve regeneration. Materials and methods: This research is an experimental study. Forty eight male rats (200-250 gr) were used. After axotomy, 1 cm segment of the sciatic nerve in rats was resected, and the gap was then bridged by one of the four methods (polyvinylidene fluoride or PVDF + Collagen gel, Autograft, Sham and Control). All animals were evaluated at 7, 21, 35, 46, 60 and 90 days after operation by sensory test, sciatic functional index (SFI) and at 90 days by electrophysiologic testing. Sciatic nerve was studied by light and electron microscope after 4 and 12 weeks of implantation.Findings: At 90 days after operation, there was no difference in sensory testing between groups. The mean SFI at the 9 weeks, in autograft group was superior to that of Collagen gel + PVDF group (P<0.01). Mean motor nerve conduction velocity in the difference between experimental groups was not significant (P=0.05). After 4 weeks of implantation, regenerated tissue cables into PVDF tube were round shaped and the mean number of myelinated axons in Autograft group was superior to that of Collagen gel + PVDF group (P<0.001). Mean number of myelinated axons in Collagen gel + PVDF group were lower than autograft group (P<0.01), after 12 weeks of implantation.Conclusion: The positive effects of collagen gel on regeneration of nerve through a PVDF channel seen in this study suggest that it may by useful for treating peripheral nerve injuries.