Papers by Keyword: PVDF

Abstract: This study aims to increase the efficiency of Li ion recovery via electrodialysis technique by manipulating several parameters. The membrane used for this study consists of a polymer matrix that acts as a backbone, and a metal organic framework (MOF) that acts as the cation selective agent. Polyvinylidene fluoride (PVDF) was chosen for this study due to its mechanical properties and chemical stability. UIO-66 was chosen as the cation selective MOF and prepared via hydrothermal method and characterized using XRD. The membrane matrix was synthesized using phase inversion casting technique. After casting, the membrane was characterized using XRD and FTIR to ensure that the MOF was successfully embedded. The investigated operation parameters are voltage applied, initial Li ion concentration, and time of operation. The tests were conducted at a selected value of each other controlled variable while manipulating only one variable at a time. The studied concentrations were 100, 200, 300, and 400 ppm, while the applied voltage varied from to 10 to 40 V with a 10 V step. The time parameter studeid was 1, 2, 3, and 4 hrs. This study aims to show the parameters’ effects on the recovery of the lithium ion. The highest recovery was recorded for each parameter.

Abstract: Using machine learning (ML) approaches for the design and manufacturing of materials becomes an emerging technology that may possibly allow us to systematically discover novel materials with promising electromagnetic interference (EMI) shielding properties. Herein, we explored the correlation between input variables such as MXene loading, thickness of nanocomposites films, frequency, and predicted EMI shielding effectiveness (ES) of poly (vinylidene fluoride)/MXene (PVDF/MXene) nanocomposites materials via ML. Two different models of ML including Gaussian process regression (GPR) and support vector machine (SVM) were considered and compared. The results showed that the predicted data by the two models are in good agreement with the experimental values, indicating that the developed ML models are appropriate for predicting properties of nanocomposites materials for EMI shielding applications.

Abstract: The application of piezoelectric polyvinylidene fluoride (PVDF) has become of a great interest. Due to its piezoelectric properties, PVDF is used in various applications, namely, microdevices and sensors. Electrospinning was found to be the most suitable and efficient method to synthesis PVDF nanofibers. It is used to obtain PVDF nanofibers without additional mechanical stretching and with high β phase content. For these reasons, it is considered to be an economic technique. In the present paper, the parameters affecting the synthesis of PVDF nanofibers such as solution concentration, flow rate, voltage and Tip to Collector Distance (TCD), have been investigated. The optimum conditions were found to be 18% concentration, 15 cm TCD, 1 mL/h flowrate and 19 kV voltages. The fabricated nanofiber has been characterized using SEM, FTIR, XRD and a conductivity test.

Abstract: This work aimed to compare the characteristics of micro and nanofibers of the poly (vinylidene fluoride) - PVDF polymer obtained by the Solution Blow Spinning (SBS) method, and films with those produced by other techniques, such as: casting and hot pressing. Thermogravimetric analysis (TGA) revealed that the films are thermally stable up to a temperature of 420 ° C. X-ray diffractometry (XRD) indicated the presence of the crystalline phases α and β, the β phase being more evident for nanofibers and PVDF casting. The film obtained by SBS showed a greater contact angle, showing to be more hydrophobic. Strain tests showed that the nanofiber films showed a 72% rupture to rupture, about 1.7 and 3.1 times greater than those obtained by casting and hot pressing, respectively. There was also a decrease in the modulus of elasticity and the limit of tensile strength of nanofibers, compared to other films.

Abstract: Precious metal Pd are widely used in high-tech industries due to their scarcity and special properties. In this paper, 2-methylimidazole zinc salt (ZIF-8)/PVDF hybrid membrane was successfully synthesized by self-assemble method. The effect of polyarcylic acid sodium (PAAS) and polyethyleneimine (PEI) as complexing agents was investigated. The rejection rate of hybrid membrane under different polyelectrolyte-metal complexing ratios and their extraction performance under different concentration were examined.

Abstract: To date, flexible, sensitive and biocompatible pressure sensors for fluctuation signals in human body have been mainly demonstrated for detecting body and muscle motion, pulse rate, heart rate and arterial blood pressure. However, because of the lack of sufficient sensitivity and flexibility, pulse signals with relatively low intensity cannot be identified and captured, such as signals derived from microcirculation in human body. As confirmed and validated by researchers, once PVDF and its copolymer based nanocomposite sensing material are applied in piezoelectric sensors, its sensitivity and piezoelectricity are highly relevant. Therefore, as one of the most effective methods to improve the permittivity and piezoelectricity of PVDF and its copolymer based nanocomposite, the effect of increasing the content of β-phase crystal was investigated in this work. In this project, the sensor possessing a novel sensing layer with the nanofiller was investigated and fabricated. The proposed sensor was designed in a simple but efficient sandwich structure. The sensing layer of the proposed sensor was made of polyvinylidene fluoride (PVDF) and polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) based nanocomposite with Zinc Oxide (ZnO) nanostructure acting as a filler portion which was fabricated by the method of Chemical Bath Deposition (CBD). The fabricated nanocomposite sensing layers were characterized. The microstructures and morphologies of pristine PVDF (P), PVDF-TrFE (PT), PVDF/ZnO (P/Z) and PVDF-TrFE/ZnO (PT/Z) with different concentration were characterized by Scanning Electron Microscope (SEM). The degree of crystallinity for P, PT, P/Z and PT/Z was obtained by X-ray Diffraction meter (XRD). In conclusion, PT exhibited better performance in both morphology and crystallinity as a sensing membrane material. More β‐phase in PT was obtained than that in P. ZnO, as a semiconductor filler, would have substantial influence on enhancing the dielectric constant by acting as a nucleating agent and forming a nanostructure with large aspect ratio.

Abstract: Fuel cell is one of the future alternative energy sources. Commercial fuel cell membrane currently used is Nafion which has several disadvantages including low stability at high temperature, and low conductivity at low humidity. Therefore, it is necessary to study an alternative membrane for PEMFC. The purpose of this research is to synthesis an alternative fuel cell membrane from sulfonated PVDF doped with nanocomposites of natural zeolite of Cipatujah, West Java, Indonesia and TiO₂ nanoparticles. The synthesis of zeolite-TiO₂ nanocomposites was performed by sol-gel method using TEOT and zeolite of Cipatujah. The nanocomposites were added to PVDF in DMSO solvent prior to ultrasonification for 1, 2 and 3 hours. The membrane was casted and sulfonated with concentrated sulfuric acid for 4, 6 and 8 hours. The membrane was characterized with FTIR, SEM-EDX, and four-point probe spectroscope. The FTIR analysis shows the existence of sulfone in the polymer. The SEM-EDX results show that the SiO₂ from the zeolite and TiO₂ have been successfully inserted to the membrane. The conductivity analysis shows that the best membrane conductivity, 0.00389 S/cm was achieved for 6 hours sulfonation and 3 hours ultrasonication.

Abstract: 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.

Abstract: This work deals with the determination of basic waterproofing properties of nanofiber textiles with basis weights of up to 30 g/m². Samples used in this experiment were made from nanofiber textiles based on two polymers – PVDF and PUR. Each polymer was prepared in three basis weights. All samples were not treated prior to testing. One of the key properties was the contact angle of water and the resistance to penetration of liquid water. Water-resistance of nanofiber textiles was tested according to the harmonized European standard EN 13859-1., Underlays for discontinuous roofing in pitched roof constructions are tested according to this standard. In the position of underlays there has to be some layer with low diffusion resistance of water vapor and relatively high waterproofing. We suppose such properties of nanofiber textiles. Testing of the two groups of material basis shows correlation between the contact angle and water-resistance of the nanofiber textile.

Abstract: We investigated the effect of poly (vinylidene fluoride) (PVdF) binder content on graphite negative electrodes for lithium secondary batteries. The negative electrode was prepared by artificial graphite powder and poly (vinylidene fluoride) binder. Scanning electron microscopy, charge/discharge test, and electrochemical impedance microscopy were conducted. As a result of electrochemical analysis, we confirmed that the electrochemical behavior varied according to the PVdF content (5, 10, 15, 50, and 90 wt%). In addition, charge/discharge test and electrochemical impedance microscopy results showed the high irreversible capacities and resistances, observed for electrodes containing PVdF contents of 50 and 90 wt%. This demonstrated that decomposition of the binder was generated during electrochemical analysis.