Effect of Nanostructures Addition and Enhancement of Poly (Vinylidene Difluoride) (PVDF) Energy Harvesting

With concerns in energy crisis and global warming, researchers are actively investigating alternative energy renewable solutions. Among the various methods, piezoelectric transduction stands out due to its impressive electromechanical coupling factor and coefficient. As a result, piezoelectric energy harvesting has garnered significant attention from the scientific community. In this study, we explored methods to enhance the piezoelectric properties of polyvinylidene fluoride (PVDF) through two distinct approaches. The first approach involved applying external high voltages at various stages during the mixture reaction. The goal was to determine whether this voltage application could alter or enhance PVDF’s piezoelectric conformation by improving the alignment of polarized dipoles. In the second part of our study, we investigated the effects of incorporating various nanostructures (including Iron Oxide, Magnesium Oxide, and Zinc Oxide) into PVDF. To analyze changes in PVDF’s crystalline structure, we utilized Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) techniques. Additionally, we measured the electric polarization of samples using a Precision LC Meter and examined the morphology of nanofibers through Scanning Electron Microscopy (SEM).

Symmetric Ferroelectric Switching in Ferroelectric Vinylidene Fluoride and Trifluoroethylene Copolymer Films

We report the observation of asymmetric switching dual peaks in ferroelectric copolymer films. These dual peaks occurs when the poling electric field is just below the coercive field and can be removed by continuous application of high enough switching voltage. Our experimental observations can be explained by the injection and the redistribution of space charges in ferroelectric films.

Crystallization Behavior and Mechanical Properties of Poly(vinylidene fluoride)/multi-walled Carbon Nanotube Nanocomposites

Poly（vinylidene fluoride）（PVDF）/multi-walled carbon nanotube（MWCNT） nanocomposites were prepared by means of ultrasonic dispersion method. X-ray diffraction（XRD） results indicate that incorporating MWCNTs into PVDF caused the formation of β phase. A thermal annealing at 130 ℃ confirmed that the β phase was stable in the nanocomposites. Differential scanning calorimetry（DSC） results indicate that the melting temperature slightly increased while the heat of fusion markedly decreased with increasing MWCNT content. The tensile strength and modulus of PVDF were improved by loading the MWCNTs. The scanning electron microscopy（SEM） observations showed that MWCNTs were uniformly dispersed in the PVDF matrix and an interfacial adhesion between MWCNT and PVDF was achieved, which was responsible for the enhancement in the tensile strength and modulus of PVDE.

Poly(vinylidene fluoride)/Clay Nanocomposites by Melt Compounding

The crystalline structures, morphologies, and mechanical properties of poly（vinylidene fluoride）/clay nanocomposites were studied using X-ray diffraction（XRD）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, polarized optical microscopy（POM）, and tensile tests. The results of XRD and TEM show that organoclays are dispersed in the poly（vinylidene fluoride）（PVDF） matrix. A clay-induced crystal transformation from α-phase to β-phase of PVFD was confirmed by XRD and FTIR. Clay layers restricted the growth of spherulite. The tensile tests indicate that the tensile modulus and yield strength as well as the elongation at break decrease when clay is loaded.

RHEOLOGICAL PROPERTIES OF POLY(VINYLIDENE FLUORIDE) IN MOLTEN STATE

The theological behavior of poly(vinylidene fluoride)(PVDF)samples of different molecular weights was investigated by means of high pressure capillary rheometer and rotational rheometer.Information on the rheological properties of such materials above melt temperatures is of interest as this can lead to an improved understanding of polymer behavior in processing and fabrication technologies.Shift factors derived from time-temperature superposition showed good fit to the Arrhenius equation with a flow activa...

Fabrication of poly(vinylidene fluoride) membrane via thermally induced phase separation using ionic liquid as green diluent

Ionic liquid(IL),1-butyl-3-methylimidazolium hexafluorophosphate([BMIM]PF6)as a new and environmentally friendly diluent was introduced to prepare poly(vinylidene fluoride)(PVDF)membranes via thermally induced phase separation(TIPS).Phase diagram of PVDF/[BMIM]PF6 was measured.The effects of polymer concentration and quenching temperature on the morphologies,properties,and performances of the PVDF membranes were investigated.When the polymer concentration was 15 wt%,the pure water flux of the fabricated membrane was up to nearly 2000 L·m-2·h-1,along with adequate mechanical strength.With the increasing of PVDF concentration and quenching temperature,mean pore size and water permeability of the membrane decreased.SEM results showed that PVDF membranes manufactured by ionic liquid(BMIm PF6)presented spherulite structure.And the PVDF membranes were represented asβphase by XRD and FTIR characterization.It provides a new way to prepare PVDF membranes with piezoelectric properties.

A FACILE APPROACH FOR THE SURFACE MODIFICATION OF POLY(VINYLIDENE FLUORIDE) MEMBRANE VIA SURFACE-INITIATED ATOM TRANSFER RADICAL POLYMERIZATION

A novel approach for the surface modification of poly(vinylidene fluoride)(PVDF)membrane was successfully realized through alkaline treatment,UV-induced bromine addition,and followed by surface-initiated atom transfer radical polymerization(ATRP)of methyl methacrylate(MMA).Chemical changes on the PVDF membrane before and after modification were analyzed with attenuated total reflectance Fourier transform infrared spectroscopy(ATR/FT-IR)and X-ray photoelectron spectroscopy(XPS).Primary kinetic study revealed...

Highly efficient and stable perovskite solar cells with strong hydrophobic barrier via introducing poly(vinylidene fluoride)additive

Perovskite solar cells(PSCs)have become the promising next-generation photovoltaic devices due to their excellent photoelectric performances,and the power conversion efficiencies(PCEs)have experienced unprecedented rapid increase in recent years.However,to realize the practical application of PSCs,high performance and long-term stability are required and the preparation of high-quality perovskite film is the key.Herein,we adopt a simple and effective method to prepare high-quality perovskite films by introducing the poly(vinylidene fluoride)(PVDF)polymer additive with abundant hydrophobic F.As the growth template,the PVDF promotes the growth of perovskite crystal,improves the crystallinity and film morphology,thus reducing defect density and inhibiting carrier recombination.The results show that the photovoltaic performances of the perovskite device with PVDF are meaningfully improved,and a high PCE of 21.42%is achieved with an improvement of 10.87%,More importantly,the PVDF-based perovskites display greatly enhanced humidity and heat stability due to the protection of strong hydrophobic barrier from F and PVDF long chain.Aging at 45%±5%relative humidity(RH)for 2400 h and 850 C for300 h,respectively,the unsealed PVDF devices can maintain over 90%of the initial PCE.It indicates that suitable polymer additives can improve the film quality to acquire high-performance and stable PSCs and lay a foundation to design new perovskite light absorption layer with different polymers for the further development of PSCs.

Molecular Modulation of Structure and Ferroelectric Performance of Poly(vinylidene fluoride)Free Standing Films from Aspects of Molecular Weight and Crystallization Temperature

Ferroelectric polymer poly(vinylidene fluoride)(PVDF)has received great research interest because of its special electroactive properties which are strongly dependent on the crystalline structures and in turn processing conditions.The effect of molecular weight and crystallization temperature on the micro-structure and macro-properties of PVDF films casted from dimethyl sulfoxide(DMSO)solvent is investigated.The results demonstrated that a low molecular weight(180 kg/mol)and a low evaporation temperature(50℃)favored the formation of polarγ-phase,while a high molecular weight(1000 kg/mol)and a high evaporation temperature(125℃)made PVDF crystallize intoα-phase.Compared with films casted at 50℃,films casted at 125℃exhibited higher dielectric loss at a low electric field and less loss conductivity at a high electric field,which was due to their low degrees of crystallinity and fine evaporation of the solvent,respectively.PVDF with a molecular weight of 180 kg/mol casted at 125℃exhibited the highest remnant polarization(0.062 C/m^(2))among all of the solution-processed films,being a result of high chain mobility resulted from the low molecular weight.

High permeability poly(vinylidene fluoride)ultrafiltration membrane doped with polydopamine modified TiO_(2) nanoparticles

In order to improve the water permeability of poly(vinylidene fluoride)(PVDF)ultrafiltration(UF)membranes with low molecular weight cut-off(MWCO),polydopamine(PDA)was employed in the membrane preparation process.Owing to itsmerits of material-independent adhesion,PDAwas coated on inorganic particles or added in coagulation bath to tailor the final membrane structure and property.The introduction of PDA broke through the permeability/selectivity trade-off of the PVDF membrane.By adding the PDA coated titaniumdioxide(PDA/TiO2)nanoparticles,water flux increased by 287% while MWCO kept similar with the pristine PVDF membrane.Thermodynamics and Kinetics of the PVDF/additives/non-solvent were analyzed and shown that nanoparticles reduced the thermodynamic stability and increased the phase separation speed,and the speed can be adjusted using different nanoparticles.Additionally,X-ray diffraction(XRD)test indicated that PVDF crystalline form changed fromαphase to β phase after adding different nanoparticles.Permeability/selectivity trade-offwas broken through by DA addition in coagulation bath.Compared with the original PVDF membrane,when the DA concentration of the coagulation bath was 2.0 g·L^−1,water flux increased by 312%,and MWCO of the PVDF membrane ranged in 10,000 to 20,000 Da as well as contact angle decreased from 81.4°to 45°.

Determining the degree of grafting for poly(vinylidene fluoride) graft-copolymers using fluorine elemental analysis

Acrylic acid (AAc) and styrene (St) were grafted onto poly(vinylidene fluoride) (PVDF) powder or membrane samples by pre-irradiation graft copolymerization.The grafted chains were proved by FT-IR spectroscopy analysis.The degree of grafting (DG) of the grafted PVDF was determined by fluorine elemental analysis (FEA) method,and was compared with the DGs determined by weighing method,acid-base back titration method and quantitative FT-IR method.The results show that the FEA method is accurate,convenient and universal,especially for the grafted polymer powders.

Effects of Stretching Ratio and Temperature on Phase Transition of Melt-spun Poly(Vinylidene Fluoride) Fibers

The effects of stretching ratio and stretching temperature on pbase transition of melt-spun poly （ vinylidene fluoride ） fibers were investigated and analyzed by using scanning electron microscopy, wide angle X- ray diffraction, differential scanning calorimetry and Fourier transfer infrared spectroscopy. The β phase exists in the as-spun fiber. The β phase content increases as the stretching ratio increases. When the stretching temperature is lower than 100 ℃ , enhancing temperature is good for the transition of phase a to ft. By contrast, when the stretching temperature is higher than 100 ℃ , enhancing temperature is unfavourable for the transition of phase a to β. Increasing the draw temperature increases the α-phase content.

EFFECT OF GAS FLOW RATE ON CRYSTAL STRUCTURES OF ELECTROSPUN AND GAS-JET/ELECTROSPUN POLY(VINYLIDENE FLUORIDE)FIBERS

The effect of gas flow rate on crystal structures of electrospun and gas-jet/electrospun poly(vinylidene fluoride) (PVDF) fibers was investigated.PVDF fibers were prepared by electrospinning and gas-jet/electrospinning of its N,N-dimethylformamide (DMF) solutions.The morphology of the PVDF fibers was investigated by scanning electron microscopy (SEM).With an increase of the gas flow rate,the average diameters of PVDF fibers were decreased.The crystal structures and thermal properties of the PVDF fibers were...

Fabrication of Poly(vinylidene fluoride) /Polysulfone Flat Blend Membranes via Thermally Induced Phase Separation Process for Water Treatment

Poly(vinylidene fluoride) /polysulfone(PVDF/PSF) flat blend membrane was prepared via thermally induced phase separation(TIPS) technique.The membrane formation mechanism and membrane structure were investigated and the effects of PSF/PVDF weight ratio on morphology,crystallinity,porosity,and mechanical properties of the membrane were discussed.The relationship between membrane structure and performances,such as pure water flux and the rejection of carbonic black,was also discussed.It was found that solid-liquid(S-L) phase separation occurred for the PVDF/PSF/diluent system.The addition of PSF influences structure and crystallinity of the membrane,which in turn influences mechanical properties and performances of the membrane.The results reveal that it is possible to obtain network structure via S-L phase separation by blending the polymer,which has a partial compatibility with PVDF.

The Effects of Radiationon Crystal Transformationsof Poly（vinylidenefluoride）

his paper covers the effects of γ-radiation on crystal transformations of Poly-(vinylidene fluoride)before and after drawing as well as during annealing process.The results show that the drawing results in a drastic increase in both crystallinityalong the meridian direction and β-form crystal content for the irradiated samples.When the drawn samples were irradiated under appropriate dose and then annealedat 140℃ , transformation from β-form to a-form was subjected to an inhibition.The transformation mechanisms between the two types of crystals are discussed onthe basis of results of WAXD and DSC.

Preparation and characterization of the antifouling porous membranes from poly(vinylidene fluoride)-graft-poly(N-vinyl pyrrolidone) powders

Porous membranes were prepared using the phase inversion method from poly(vinylidene fluoride)-graftpoly(N-vinyl pyrrolidone)(PVDF-g-PVP) powders, which were synthesized via γ-ray induced graft polymerization(pre-irradiation). Chemical compositions, thermal behavior, morphology and hydrophilicity of the membranes were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, element analysis, thermalgravimetric analysis, differential scanning calorimetry, scanning electron microscopy and contact angle measurements, respectively. Permeation experiments were conducted to evaluate the water flux,and the dynamic BSA fouling resistance performances were investigated, too. All the experimental results indicate that the PVDF-g-PVP membranes demonstrate better separation performances over the pristine PVDF membrane.

Effect of Calcination Temperature on La-Modified Al2O3 Catalysts for Vapor Phase Hydrofluorination of Acetylene to Vinyl Fluoride

A La-modified Al2O3 catalyst was prepared with deposition-precipitation method. The effect of calcination temperature on the reactivity for vapor phase hydrofluorination of acetylene to vinyl fluoride. The catalysts calcined at different temperatures were characterized using NH3-TPD, pyridine-FTIR, X-ray diffraction, and Raman techniques. It was found that the calcination process could not only change the structure of these catalysts but also modify the amount of surface acidity on the catalysts. The catalyst calcined at 400 ℃ exhibited the highest conversion of acetylene （94.6%） and highest selectivity to vinyl fluoride （83.4%） and lower coke deposition selectivity （0.72%）. The highest activity was related to the largest amount of surface acidity on the catalyst, and the coke deposition was also related to the total amount of surface acidic sites.

A comparative study for petroleum removal capacities of the bacterial consortia entrapped in sodium alginate,sodium alginate/poly(vinyl alcohol),and bushnell haas agar

The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different polymers such as Sodium Alginate(SA),Sodium Alginate/Poly(Vinyl Alcohol)(SA/PVA),and Bushnell Haas Agar(BHA).In addition to SA and SA/PVA,which are cost-effective,non-toxic and have different functional groups,BHA,which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until now.Based on these,the polymers with different surface morphologies and chemical compositions were analyzed by SEM and FT-IR.While the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one,BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/PVA.Accordingly,the degradation rate of bacterial consortia entrapped with BHA was 2.039 day^(-1),SA/PVA was 1.560,SA was 0.993,the half-life period of BHA-entrapped bacterial consortia is quite low(t_(1/2)=0.339)compared with SA(t_(1/2)=0.444)and SA/PVA(t_(1/2)=0.697).The effects of the four main factors such as:amount of BHA(0.5,1,1.5,2,2.5,3 g),disc size(4,5,6,7,8 mm),inoculum concentration(1,2.5,5,7.5,10 mL),and incubation period on petroleum removal were also investigated.The maximum petroleum removal(94.5%)was obtained at≥2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical analysis.Although a decrease was observed during the reuse of bacterial consortium entrapped in BHA,the petroleum removal was still above 50%at 10th cycle.Based on GC-MS analysis,the removal capacity of BHA-entrapped consortium was over 90%for short-chain n-alkanes and 80%for medium-chain n-alkanes.Overall,the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the future.Since there has been no similar study investigating petroleum removal with the bacterial consortia entrapped with BHA,this novel entrapment material can potentially be used in the treatment of petroleum pollution in advanced remediation studies.

Rare Earth Stearates as Thermal Stabilizers for Rigid Poly(vinyl chloride)

A series of stearates with different rare-earth ion were investigated as thermal stabilizers for rigid PVC at 180 ℃ in air. Their stabilizing efficiency was based on measuring the rate of dehydrochlorination. The resulted revealed the higher stabilizing efficiency of the investigated rare-earth stearates as thermal stabilizers for rigid PVC compared with the thermal stabilizers for industry: calcium stearate, zinc stearate, butyl stannum mercaptide, phosphite esters, β-diketone and epoxidized sunflower oil. This was well illustrated by longer incubation period (T_S) values and lower rate of dehydrochlorination. The stable efficiency was affected by the nature of rare-earth element's individual electronic shell. The mechanism for the stabilizing effect of rare-earth stearates was proposed. The result was experimentally proved based on IR spectrum.

Controlled delivery of ibuprofen from poly(vinyl alcohol)-poly(ethylene glycol) interpenetrating polymeric network hydrogels

Hydrogels composed of poly(vinyl alcohol)(PVA) and poly(ethylene glycol)(PEG) were synthesized using glutaraldehyde as crosslinker and investigated for controlled delivery of the common anti-inflammatory drug, ibuprofen(IBF). To regulate the drug delivery, solid inclusion complexes(ICs) of IBF in β–cyclodextrin(β–CD) were prepared and added to the hydrogels. The ICs were prepared by the microwave irradiation method, which is more environmentally benign. The formation of IC was confirmed by various analytical techniques and the synthesized hydrogels were also characterized. Controlled release of drug was achieved from the hydrogels containing the ICs in comparison to the rapid release from hydrogels containing free IBF.The preliminary kinetic analysis emphasized the crucial role of β–CD in the drug release process that influences the polymer relaxation, thereby leading to prolonged release. The cytotoxicity assay validated the hydrogels as non-toxic in nature and hence can be utilized for controlled delivery of IBF.