Performance Of Polyvinylidene Fluoride Research Articles

Highly durable triboelectric nanogenerators based on fibrous fluoropolymer composite mats with enhanced mechanical and dielectric properties

Recent advances in the field of energy harvesting suggest the importance of nanostructured porous materials in improving the performance of triboelectric nanogenerators (TENGs). Due to their high surface-to-volume and unique nanostructure assembly, they have been used for development of high-performance TENGs. Nevertheless, due to their insufficient mechanical integrity, they are vulnerable to mechanical friction, and thus have encountered a bottleneck to retain their performance in many cycles. To address this, we have introduced an approach to design highly durable TENGs based on fibrous composite via a facile process. Systematic study was conducted to explore incorporation of different carbon-based nanofillers (graphene nanoplatelets [GnPs], carbon nanotubes [CNTs], and carbon nanofibers [CNFs]) on performance of polyvinylidene fluoride (PVDF) fibrous mats. Among different nanofillers, incorporation of GnP can significantly enhance various characteristics of composites. The developed PVDF-GnP fibrous composite sample with 1 wt% nanofiller content was then used as the tribonegative material in TENG structure. Designed TENG displayed outstanding performance, with the output voltage and current of 134.4 V and 12.9 μA, respectively. Moreover, fibrous PVDF-GnP composite retained structural characteristics, and no deterioration was observed after over 350,000 cycles. Overall, the outstanding triboelectric performance of developed fibrous composites, along with their superior mechanical and electrical properties, make them ideal candidate for development of durable high-performance TENGs.

Effect of hexagonal-boron nitride nanosheets (h-BNNSs) on the structural morphology and performance of polyvinylidene fluoride (PVDF) membranes for water-oil separation

Hexagonal-boron nitride nanosheets/polyvinylidene fluoride (h-BNNSs/PVDF) composite membranes were successfully fabricated through a facile one-step phase inversion process. The amount of h-BNNSs incorporated into the PVDF membranes was varied within the mass percent range of 0–3 %, and the influence of the membranes' structural properties on water-oil separation was investigated. Surface roughness and wettability analyses (water contact angle data) showed that the membranes are hydrophilic, and the average surface roughness measurements reveal that the presence of h-BNNSs enhances the wettability of the composite membranes. In addition, h-BNNSs in composite membranes increased the total porosity which favoured enhanced membrane separation flux. Scanning electron microscopy investigations revealed flat surfaces with porous structures, sponge-like morphology and granular-like porous structures. The performance of the composite membranes for water-oil separation revealed that the addition of h-BNNSs to the membrane polymeric matrix resulted in enhanced selectivity towards water with the highest flux of 384.96 L/m2h, and selectivity efficiency of 99.60 % for a 3 % h-BNNSs/PVDF composite membrane, with no transmembrane pressure applied. The preference for water as a filtrate is attributed to the superior water permeation properties of the h-BNNSs and PVDF interaction. Water permeability was due to the presence of positively charged B atoms which pull the oxygen atoms in the water molecules. The improvement in fluxes of the investigated membranes, upon the addition of h-BNNSs makes them excellent candidates for water-oil emulsion separations.

Polyvinylidene fluoride—An advanced smart polymer for electromagnetic interference shielding applications—A novel review

AbstractEmerging technology and modernization have become a worldwide threat to human life in all aspects. Worldwide, all countries are in the race to develop the most advanced electronic devices and gadgets as they reflect the country's superiority and economic development. Specialists have forecasted that during and after the pandemic, the addiction toward modern gadgets have increased by 40% among the people irrespective of age. A few researchers have reported that the world economy is dependent on and dominated by countries manufacturing semiconductors, mobiles, electronic chips, and so on. People started sensing that modern devices are like a boon, as their lives seem to be more connected and comfortable with all their needs and wants being fulfilled at their doorsteps. But this boon is slowly whirling as a severe threat to human lives. Due to this rapid usage of electronic devices, electromagnetic interference (EMI) is drastically growing, which is considered a global warning issue for commercial and biological systems. So advanced countries have decided to make EMI shielding a compulsory entity to be implemented in all advanced electronic devices. Though traditional materials like metals and carbon allotropes have excellent shielding properties, they cannot cope with today's mass production of modern devices. Thus, researchers had to find a suitable substitute material that should possess properties such as sustainability and biocompatibility to overcome problems faced by the conventional materials. Thus, polymers have come into the world of EMI shielding applications. Polyvinylidene fluoride (PVDF), a non‐conductive polymer from the family of Fluorocarbons, is creating history in the field of EMI shielding applications. PVDF astonished researchers with its versatile features, such as light weight, flexibility, and easy processibility with excellent dielectric and piezoelectric properties. Though they are poor in electrically conductive properties, incorporating metals, carbon allotropes, and metal oxides as fillers make them superior to the existing conventional materials. Thus, the main objective of this review article is to highlight the uniqueness of PVDF as an advanced polymer for EMI shielding applications. It has been noted that PVDF is more suitable for EMI shielding in X, K, and Ku band frequencies. But overall, we noticed that the performance of PVDF has a great impact by incorporating a combination of metal and carbon allotrope enhances the shielding effectiveness up to 65 dB in the Ku‐band (Kurz‐under) frequency band range of (12–18 GHz).

The impact of PET microplastic fibres on PVDF ultrafiltration performance – A short-term assessment of MP fouling in simple and complex matrices

Wastewater treatment plants (WWTPs) are key components for the capture of microplastics (MPs) before they are released into natural waterways. Removal efficiencies as high as 99% may be achieved but sub-micron MPs as well as nanoplastics have been overlooked because of analytical limitations. Furthermore, short MP fibres are of concern because of their low capture rate as well as the lack of understanding of their influence on purification system efficiency. This study has investigated the impact of poly(ethylene terephthalate) (PET) short nanofibres on the performance of polyvinylidene fluoride (PVDF) ultrafiltration membranes during cross-flow operation. Model MP fibres with an average length of 10 ± 7 μm and a diameter of 142 ± 40 nm were prepared via a combination of electrospinning and fine cutting using a cryomicrotome. The manufactured MPs were added to both pure and synthetic domestic wastewater at a concentration of 1 mg.L−1 to determine their impact on the performance of PVDF ultrafiltration membranes. The results show that PET fibres attach to the membrane in a disorganised manner with low pore coverage. The water flux was decreased by 8% for MPs in pure water and no noticeable effect in wastewater after 3 days of filtration. Additionally, the nutrient removal efficiency of the membrane was not altered by the presence of PET MPs. These findings show that MP fibres do not significantly influence the early stages of filtration for a standard concentration of MPs in wastewater treatment plant studies.

Aging of polyvinylidene fluoride (PVDF) ultrafiltration membrane due to ozone exposure in water treatment: Evolution of membrane properties and performance

Pre-ozonation is an effective pretreatment tactic for mitigating fouling of ultrafiltration (UF) membrane in water and wastewater treatment, but the compatibility of polymeric UF membranes with residual ozone remains unclear. In this study, effects of long-term ozone exposure on properties and performance of polyvinylidene fluoride (PVDF) UF membrane reinforced by polyethylene terephthalate (PET) layer were systematically investigated. The exposure intensities were designed to simulate ozone exposure at 0.1 mg/L for 0.5–5 years. Chemical composition analysis suggested that the hydrophilic additives, such as possibly polyvinyl pyrrolidone (PVP), was gradually degraded and released from the membrane, whereas the PVDF matrix exhibited fairly good ozone resistance. Ozonation resulted in increase of pore size and decrease of surface hydrophilicity, which can be attributed to oxidation and dislodgement of hydrophilic additives. Accordingly, long-term ozonation led to moderate changes in performance factors, including increase of membrane permeability by 34%, decrease of retention ability by 21.8%, increase of organic fouling propensity. It is worth noting that membrane tensile strength suffered substantial decrease after ozonation, probably due to ozonation of the PET support layer. Overall, it seems that the PVDF functional layer exhibited good ozone resistance, but the PET support layer was the Achilles' heel of the reinforced PVDF membrane for integrating with pre-ozonation.

Surface free energy, microstructure and performance of polyvinylidene fluoride (PVDF) membrane: the influence of hydrophilic porogens

Polyvinylidene fluoride (PVDF) membrane are widely used in water treatment due to its good physical and chemical properties, and the pores of PVDF membranes determine most of the characteristics of PVDF membrane. The hydrophilic porogens play an important role in the preparation of PVDF membranes and the regulation of membrane pores. In this work, three hydrophilic porogens with different quality components were used to prepare PVDF ultrafiltration membranes by the nonsolvent induced phase separation (NIPS) method. Through the Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), mechanical strength, contact angle and other characterizations, the influence of hydrophilic porogens on the surface free energy, microstructure and performance of PVDF membrane were studied. The results suggest that lithium chloride (LiCl) can inhibit the formation of macropores and improve the mechanical strength of the membrane. Polyvinylpyrrolidone (PVP) can form through-hole through the PVDF membrane. All three hydrophilic porogens can increased the surface free energy of the PVDF membranes, where polyethylene glycol (PEG) had the most impact on the surface free energy.

Rice husk ash and Zr-MOF nanoparticles improve the properties and ultrafiltration performance of PVDF nanomembranes

Herein we demonstrate the effects of rice husk ash (RHA) and two Zr-metal organic frameworks (MOFs; OPA-UiO-66 and OPA-UiO-66-SO3H) nanoparticles on the properties and performance of polyvinylidene fluoride (PVDF) composite membranes. The nanoparticles and PVDF dope were pre-blended and fabricated as thin-film nanomembranes via soft lithography. The new membranes had uniform pore structures and demonstrated high permeability and durability. Improved tensile strength was associated with increased β crystalline formation of the PVDF, with the greatest increase observed for PVDF/RHA due to the high silica content of the RHA. RHA increased membrane hydrophilicity whereas the MOFs increased hydrophobicity. In ultrafiltration, the new membranes exhibited superior performance compared to conventional PVDF composite membranes made with titanium oxide and nanoclay. High rejection rates and significantly improved antifouling properties were achieved in both PVDF/RHA and PVDF/MOF membranes for high concentration aqueous solutions of sulfamethoxazole, bovine serum albumin, and SARS-CoV-2. This improved performance was attributed to multiple functional groups in RHA and MOFs that promote various surface interactions between contaminants and PVDF membranes. The new high-performance nanomembranes have potential applications in separation and purification processes, biosensing, and in personal protective equipment.

Morphology and performance of polyvinylidene fluoride (PVDF) membranes prepared by the CCD method: Thermodynamic considerations

The combined crystallisation and diffusion method (CCD) has recently demonstrated its superiority in producing high-performance PVDF membranes over the traditional membrane preparation methods. The CCD method involves a unidirectional cooling step in its membrane preparation. While the role of kinetics behind the CCD method has been thoroughly studied by varying the cooling rate, the cooling temperature itself has never been changed from −30 °C. This study therefore explores the thermodynamic implications of changing the cooling temperature during the CCD process on the morphology and performance of the resultant membranes. Two different molecular weights of PVDF were studied and different batches of membranes were prepared by progressively changing the cooling temperature from −30 °C to 0 °C. The results showed that for both the PVDF types, with an increase in cooling temperature, the separation surface pore sizes and membrane permeances increase but more so for the one prepared using the higher molecular weight PVDF. This showcases the ability to tailor the properties of the CCD membranes by merely changing the cooling temperature. The membranes were then also characterised for their morphology, mechanical strengths and crystallinity to help further understand the role of cooling temperature in affecting these membrane properties.

Polyvinylidene Fluoride/Nanoclays (Cloisite 30B and Palygorskite) Mixed Matrix Membranes with Improved Performance and Antifouling Properties

In this study, it was attempted to prove the effectiveness of nanoclays as economical and nontoxic nanofillers through comparison with carbon nanotubes (CNTs). Two hydrophilic nanoclays, namely, Cloisite 30B and palygorskite (PGS), were used as nanofillers to improve the morphology and performance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes. A nonsolvent-induced phase separation (NIPS) method was used to prepare mixed matrix membranes (MMMs). The effects of the nanoclays on morphology, performance, and antifouling properties of the prepared MMMs were investigated. It was found that compared to PVDF membranes, the hydrophilicity, antifouling properties, and morphology of the fabricated MMMs are improved significantly. Compared to PVDF membranes, pure water flux (PWF) values of the MMMs containing the optimum contents of Cloisite 30B (0.5 wt %) and palygorskite (1 wt %) improved by 44.7 and 61.7%, respectively. Acid-treated CNTs were used as a reference additive, and the performance and antifouling properties of the prepared PVDF/nanoclay MMMs were compared with the prepared PVDF/acid-treated CNT MMMs. It was found that the PWF values of the MMM containing optimum contents of PGS and Cloisite 30B nanoclays are 86 and 77%, respectively, compared with that of the MMM containing acid-treated CNTs. The PVDF/Cloisite 30B MMM exhibited lower PWF than the PVDF/PGS MMM, which could be attributed to the plate-like structure of Cloisite 30B. Also, the flux recovery ratio (FRR) values of the mixed matrix membranes containing optimum contents of PGS and Cloisite 30B nanoclays were 95.65 and 92.06%, respectively, compared to that of the MMM containing acid-treated CNTs. Also, the BSA rejections of the prepared MMMs containing optimum contents of Cloisite 30B and palygorskite were comparable with that of the MMM containing acid-treated CNTs. Therefore, nanoclays can be suggested as economical and ecofriendly nanofillers for improving the PVDF membrane performance.

Morphology control in PVDF membranes using PEG/PVP additives and mixed solvents

The effects of the mixed two solvents, Dimethylacetamide (DMAc) and Dimethylformamide (DMF), and Polyethylene glycol (PEG) and Polyvinylpyrrolidone (PVP) as additives on performance of Polyvinylidene fluoride (PVDF) membranes were studied. Initially, PEG200 was used as a primary additive at fixed percentage of 5% wt. PVP was then blended with PEG200 in different concentrations. PVDF and DMAc were used as polymer and solvent in the casting solutions, respectively. To control the diffusion rate of PVP in the presence of PEG200 and PVP blend, mixtures of DMAc and DMF were used as the mixed solvent in the casting solutions. Asymmetric PVDF membranes were prepared via phase inversion process in a water bath and the effects of two additives and two solvents on the membrane morphology, pure water flux (PWF), hydrophilicity and rejection (R) were investigated. Attenuated Total Reflection Fourier Transform Infrared Spectra (ATR-FTIR) analysis was used to show the residual PVP on the surface of the membranes. Atomic Force Microscopy (AFM) was utilized to determine roughness of membrane surface. The use of mixed solvents in the casting solution resulted in reduction of PVP diffusion rate and increment of PEG diffusion rate. Eventually, PWF and R values reduced, while porosity and hydrophilicity increased.

Effect of Adding Functionalized Graphene on the Performance of PVDF Membrane in Direct Contact Membrane Distillation

In this paper, the effect of adding modified graphene nanoplatelets (MGNPs) as a filler on the characteristics and performance of Polyvinylidene fluoride (PVDF) membrane in a direct contact membrane distillation (DCMD) configuration was investigated. Both pure PVDF and PVDF/MGNPs composite (2%) membranes were fabricated by using electrospinning technique. The fabricated membranes were characterized using different analyses techniques such as SEM imaging, XRD analysis, static water contact angle as well as membrane porosity and liquid enter pressure measurements. Also, the average fiber diameter and the average membrane pore diameter were estimated using ImageJ software. The prepared PVDF/MGNPs composite membrane exhibited lower fiber diameter by about 5.7%, whereas the contact angle increased by 10 and liquid entry pressure increased by 11.7%. The membrane also showed an enhanced flux that reached about 19.8 kg/m2∙h at feed inlet temperature of 65°C, feed flow rate of 30 l/h. and feed inlet concentration of 10000 ppm. This represents about 13.46% improvement over the pure PVDF membrane at the same conditions. The produced membrane presents a viable alternative to commercial MD membranes.

Effect of silica nanotubes on characteristic and performance of PVDF nanocomposite membrane for nitrate removal application

In this work, impact of synthesized silica nanotubes (SNTs) on morphology and performance of polyvinylidene fluoride (PVDF) nanocomposite membrane was studied. For this purpose, SNTs were synthesized using hydrothermal method, characterized by different techniques, and finally used as filler in nanocomposite membrane preparation. The PVDF/SNTs nanocomposite membranes were fabricated via phase inversion method at different dosage of SNTs (1–6 wt.%). As-prepared membranes and SNTs were characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and contact angle measurement. The results confirmed by incrementing SNTs dosage, hydrophilicity of PVDF membrane was increased. The effect of SNTs on the membrane performance was studied through nitrate removal at operating pressure of 7 bar. The results showed that the optimal performance parameters (nitrate rejection and pure water permeability (PWP) were obtained at SNTs dosage of 4%. The effect of feed concentration (50, 100, and 150 mg/L) on nitrate separation performance was also investigated and it was found that the maximum rejection of 86% and PWP of 11.58 (L/m2.h.bar) were achieved for optimum PVDF/SNTs membrane at 150 mg/L. Finally, antifouling properties of optimum PVDF/SNTs membrane were investigated.

Effect of temperature on the pulse‐echo performance of ultrasonic transducers fabricated with PVDF film

Empirical data is presented on the pulse-echo performance of poly-vinylidenefluoride (PVDF) ultrasound transducers monitored in-situ at temperatures in the range 50–130°C. Measurements were performed over a 5 h period beginning at the sensors’ initial exposure to temperature. A reduction in pulse-echo amplitude was observed at all temperatures in the range and was found to be proportional to temperature increase. Four different thicknesses of PVDF film were used for the trials and small differences in behaviour were observed between sensors constructed using each thickness. On average, the overall loss was found to increase linearly with temperature from a 16% drop in pk–pk pulse-echo voltage observed at 60°C to a 95% drop in performance at 120°C after 5 h. Rates of signal loss were found to follow a logarithmic decay, particularly at temperatures above 70°C where significant reductions were observed in the initial seconds/minutes following exposure to temperature.

Effects of pre-oxidant (KMnO4) on structure and performance of PVDF and PES membranes

The structure and performance of membrane materials are very important to the efficient and stable operation in membrane drinking water purification technology. Potassium permanganate (KMnO4), which can change the characteristics of organic matters and control membrane surface fouling, has been widely used as pre-oxidant in the front of membrane drinking water process. This study investigates the evolution of membrane surface structure and performance when polyvinylidene fluoride (PVDF) and polyethersulfone (PES) were exposed to 10, 100 and 1000 mg·L− 1KMnO4 solution for 6 and 12 d, respectively. The aged membrane physicochemical characteristics such as membrane surface morphology, chemical composition, hydrophilicity, porosity and zeta potential were evaluated by modern analytical and testing instruments. The anti-fouling property of membrane surface was also investigated by the filtration-backwash experiment. The results indicated that the different concentrations and exposure time of KMnO4 led to a different variation on PVDF and PES membrane surface structure and performance, which could further affect the membrane separation performance and the membrane fouling behaviors. The membrane surface pore size and porosity increased due to the dislodgment and degradation of membrane additive (PVP), which improved membrane permeability and enhanced the adsorption and deposition of pollutants in the membrane pores. With the increase of exposure time, the membrane surface pore size and porosity reduced for the reactions of chain scission and crosslinking on membrane materials, and the backwashing efficiency declined, leading to a more serious irreversible fouling. Compared with PVDF membranes, the formation of sulfonic group for PES membranes increased the negative charge on membrane surface due to the oxidation of KMnO4. The present study provides some new insights for the regulation of the pre-oxidant dose and the selection of the membrane materials in KMnO4 pre-oxidation combined with membrane filtration system.

Preparation and antifouling properties of PVDF ultrafiltration membranes with polyaniline (PANI) nanofibers and hydrolysed PSMA (H-PSMA) as additives

Polyaniline (PANI) nanofibers were used as hydrophilic additives to study their effect on the performance of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes. PVDF UF membranes were prepared by the phase inversion method with hydrolyzed polystyrene-co-maleic anhydride (H-PSMA) and PANI nanofibers as additives. PANI nanofibers were synthesized by rapid mixing reaction and were used as a hydrophilic modifying agent with varying concentrations (0–1.5 wt.%) in the membranes. The synthesized PANI nanofibers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis. Hydrolyzed PSMA was prepared by the hydrolysis of PSMA and was used as a novel pore forming additive. The addition of PANI nanofibers into the membranes increased the membrane hydrophilicity, porosity, water uptake and permeability. The membranes also showed good antifouling nature during BSA (bovine serum albumin) filtration when compared to the pristine membrane without PANI nanofibers. Membrane with 1.0 wt.% PANI content showed highest permeability among the synthesized membranes. The membrane having highest permeability was subjected to heavy metal ion rejection which showed high rejection of 98.52% and 97.38% for heavy metal ions Pb2+ and Cd2+ respectively.

Development of a PVDF membrane hydrophone for use in air-coupled ultrasonic transducer calibration

This work describes the use of a polyvinylidene fluoride (PVDF) membrane hydrophone for application in air-coupled transducer calibration. A one-dimensional theoretical analysis is used to demonstrate the potential and performance of PVDF as a hydrophone material over the frequency range 100 kHz to 5 MHz included in the evaluation is the influence of deposited metallic electrode layers on the sensitivity of the material. Experimental validation over the restricted range 400 kHz to 1 MHz is provided by a coplanar 0.028 mm thick membrane hydrophone in conjunction with a custom built 1-3 piezocomposite transmitter. Calibration of the membrane hydrophone is performed by employing a standard hydrophone that has been calibrated to a primary standard in a water medium. Justification for such an approach is presented within the theoretical analysis which provides a close correlation with experimental data. The generation of Lamb waves at critical angles in the PVDF and their subsequent influence on the directional response of membrane hydrophones operating in air is also addressed. A method for partial suppression of the Lamb waves, based around perforation of the membrane (either in whole or in part), is evaluated experimentally with reasonable results.