Vinylidene Fluoride Copolymers Research Articles

One-step production of 3D printed ferroelectric polymer forms using fused deposition modeling

This Letter presents the possibility of 3D print polymer forms with a ferroelectric crystal structure in a one-step process by using the fused deposition modeling method. The approach does not require any additional equipment, other than an extruder for filament production and a commercial 3D printer to fabricate ferroelectric polymer forms. By using the copolymer of vinylidene fluoride and tetrafluoroethylene as a filament for 3D printing, complex spatial structures, such as the gyroid form, are accessible. Compared to polyvinylidene fluoride, the copolymer of vinylidene fluoride and tetrafluoroethylene retains its ferroelectric properties even after melting in the 3D printing process and soldification. The x-ray diffraction investigation shows that the 3D forms are having a planar zigzag conformation on macromolecule scales, which relates to a crystal structure with ferroelectric properties. Annealing the 3D forms at a temperature of 110 °C for 12 h does not cause any changes to the spatial polymer structures but leads to an increase in the degree of crystallinity by more than 20%. This result contributes to an increase in the ferroelectric crystalline phase content by ∼17% and the Curie temperature by ∼7 °C in contrast to non-annealed 3D forms.

Fluoropolymer impregnated graphite foil as a bipolar plates of vanadium flow battery

Renewable energy in recent years plays an increasingly important role in the energy industry. Therefore, the problem of inventing efficient and affordable energy storage devices is of current importance. Vanadium redox flow battery stands out between a wide range of various chemical sources of electric energy. Discovering the way for optimizing the price of energy storage is one of the most important questions of the mentioned battery. New graphite-polymer composite materials study shows that they may become a replacement for commonly used brittle graphite. The current article presents the study of graphite foil (or flexible graphite) filling with a copolymer of tetrafluoroethylene and vinylidene fluoride F-42 properties. The article uses an implementation approach of putting the fluoropolymer into the pores of graphite foil, which shows a slight decrease in electrical conductivity, while a significant increase in its electrochemical stability in comparison with untreated graphite foil. Testing results of such material as current collectors (or bipolar plates) in a single membrane-electrode assembly of vanadium redox flow battery cell show peak value of discharge power density of 843 mW/cm2, energy efficiency of 78%-79% during cycling at 200 mA/cm2 allowing us to assume the possibility of its successful application in redox flow battery stacks.

Novel single-ion conducting electrolytes based on vinylidene fluoride copolymer for lithium metal batteries

A single-ion polymer electrolyte (SIPE) based on PVDF-based random copolymer (Li-PVDF) was synthesized in water from the radical copolymerization of vinylidene fluoride (VDF) with perfluoro-2-methyl-3-oxa-5-sulfonimido[-3-oxa-5-sulfonyl fluoride] vinyl ether (VEPFSIS) initiated by potassium persulfate. The purified polymer, characterized by 1H and 19F NMR spectroscopy, ICP-MS, and size-exclusion chromatography, contains 96 mol% VDF with an average molar mass of 128 kg mol−1. The Li-PVDF was cast into self-standing membranes and then swollen with a 50/50 v/v mixture of ethylene carbonate and propylene carbonate. The membrane was analyzed using DSC, TGA, pulse field gradient (PFG)-NMR and electrochemical methods. The solvent-doped membrane exhibited a lithium ion transport number close to 1 with lithium ion conductivities higher than 10−4 S cm−1 at 30 °C, an electrochemical stability up to 4.3 V vs. Li+/Li and an excellent reversibility upon continuous lithium plating/striping cycles. In addition, prototype Li/NMC battery cells using Li-PVDF as both electrolyte and cathode binder in the NMC based composite cathode showed reversible cycling and good performance at 60 °C. The results demonstrated the promising potential of this new single-ion polymer family in intrinsically safe all solid-state lithium metal based batteries.

Dielectric response of piezoelectric film structures based on a copolymer of vinylidene fluoride with trifluoroethylene and carbon nanotubes

The dielectric response of the film composite materials based on a vinylidene fluoride copolymer with trifluoroethylene and carbon nanotubes was studied. The effect of carbon nanotubes inclusions on the electrical conductivity of composite films was investigated. A qualitative model was considered to explain the results.

Multi-scale characterisation of a ferroelectric polymer reveals the emergence of a morphological phase transition driven by temperature

Ferroelectric materials exhibit a phase transition to a paraelectric state driven by temperature - called the Curie transition. In conventional ferroelectrics, the Curie transition is caused by a change in crystal symmetry, while the material itself remains a continuous three-dimensional solid crystal. However, ferroelectric polymers behave differently. Polymeric materials are typically of semi-crystalline nature, meaning that they are an intermixture of crystalline and amorphous regions. Here, we demonstrate that the semi-crystalline morphology of the ferroelectric copolymer of vinylidene fluoride and trifluoroethylene (P(VDF-TrFE)) strongly affects its Curie transition, as not only a change in crystal symmetry but also in morphology occurs. We demonstrate, by high-resolution nanomechanical measurements, that the semi-crystalline microstructure in the paraelectric state is formed by crystalline domains embedded into a softer amorphous phase. Using in situ X-ray diffraction measurements, we show that the local electromechanical response of the crystalline domains is counterbalanced by the amorphous phase, effectively masking its macroscopic effect. Our quantitative multi-scale characterisations unite the nano- and macroscopic material properties of the ferroelectric polymer P(VDF-TrFE) through its semi-crystalline nature.

Enhanced dielectric permittivity and relaxor behavior in thermally annealed P(VDF-TrFE) copolymer films

Modification of relaxor behavior and large enhancement in dielectric permittivity are demonstrated in a P(VDF-TrFE) ferroelectric polymer film by thermal annealing treatment. For coexisting normal ferroelectric and relaxor behavior in P(VDF-TrFE) (molar ratio: 45:55) films, the relative contribution from the relaxor component is increased when annealed at high temperature and subsequently quenched. A relative peak permittivity of ε′ ∼ 100 is obtained for an annealing temperature of T = 90 °C, which is one of the highest reported so far among poly(vinylidene fluoride) copolymer and terpolymer films. Based on x-ray diffraction analysis, we attribute the changes in dielectric properties to a decrease in crystallite domain size and a consequent increase in the crystalline-amorphous interfacial area.

Comparative study on the oily exudation of aluminized explosives containing EVA and F2603

In order to compare the influence of binders on the oily exudation of cyclotrimethylenetrinitramine (RDX) based aluminized explosives, polyvinyl acetate (EVA) and copolymer of vinylidene fluoride and perfluoropropylene (F2603) were selected as binders, which are most commonly used in the press-packed explosives. Herein, the binding energies of wax with the components of RDX-based aluminized explosives containing EVA and F2603 were predicted. Then, the migration models of wax in EVA and F2603 were constructed respectively, and the migration rate of wax in two binders was also calculated. Finally, experimental verification was carried out for wax migration in the two aluminized explosives. The results show that the binding energies of wax with other components of RDX-based composite explosive are all positive, which indicates that the physical compatibility of RDX-based aluminized explosives containing EVA and F2603 is excellent. In addition, wax interacts with the other components of RDX-based explosives mainly via Van der Waals force. However, the binding strength of wax with RDX crystals and binders decreases with the increase of temperature. The type of binders has a great influence on the migration rate of wax, and the oily exudation rate of wax in F2603 is about 4 times than that in EVA both at 298 K and 344 K. Meanwhile, the polymer configuration greatly changes the migration rate of wax. The calculated results are in good agreement with the experimental results.

The Effect of Mechanical Properties of Synthetic Prostheses Made by Electrospinning on the Results of Experimental Implantation in the Infrarenal Abdominal Aorta

The research aims to study the effect of circumferential compliance of synthetic vascular prostheses on their healing during implantation in the infrarenal abdominal aorta of pigs. In an experiment, 12 pigs were implanted with blood vessel prostheses in the infrarenal abdominal aorta. The prostheses possessed elastic characteristics obtained by a tensile testing machine, and differed in circumferential compliance: rigid (polycaprolactone [PCL]); less compliant than the native aorta (polyurethane [PU]); comparable in compliance to the native aorta (copolymer of vinylidene fluoride with hexafluoropropylene) before (FKM) and after radiation treatment (FKM-γ). The implanted prostheses compliance was measured by aortography during the first 3days and 1month after implantation, the condition of the prosthesis capsule was evaluated by macroscopic preparations and histologic examination. Pulsation on PCL prostheses was nonexistent immediately after implantation. On PU prostheses, slight pulsation was noted during the first 3days and disappeared after 1month. On FKM prostheses, although pulsation persisted after 1month, a significant expansion of prostheses was also recorded as a result of fatigue plastic deformation. On FKM-γ prostheses, pulsation comparable in magnitude with aortic pulsation was present 1month after implantation with no change in the size of the prosthesis. Macroscopic preparations reveal significant differences in the formed connective tissue capsule. The PCL prosthesis capsule is thick, narrowing the lumen of the vessel from the outside. The outer surface of PU prostheses is covered with a thinner uniform fibrous capsule. The inner surface of the FKM and FKM-γ prostheses is covered with a thin layer of smooth whitish tissue. The FKM prosthesis, unlike the FKM-γ prosthesis, is sharply expanded. In all cases, moderate aortic expansion was observed distal to the prosthesis. According to the histologic data, the outer and inner capsules of PCL prostheses are covered with a thick layer of fibrous tissue with signs of productive inflammation and foci of calcification. PU prostheses are surrounded by a thick connective tissue capsule partially endothelialized from the inside; the outer capsule is randomly populated with fibroblastic cells. FKM prostheses have a thin outer capsule where smooth muscle cells are visible, mainly oriented along and across the prosthesis axis; the inner capsule is thin and completely covered with a layer of endothelial cells from the side of the lumen. A layered structure is visible in the prosthesis capsule of FKM-γ, and the fibroblast cells in each layer of the capsule are oriented along or across the prosthesis axis, similar to the structure of a natural arterial vessel. The inner surface of the prosthesis is completely endothelialized. The healing and degree of inflammation in a capsule of blood vessel prostheses implanted in the infrarenal abdominal aorta of pigs depend on the degree of their circumferential compliance. Although maintaining pulsations, the cellular structure of the capsule is characterized by a greater degree of differentiation and approaches the structure of the native arterial wall.

Composite fluoropolymer piezoelectric membranes for reconstructive surgery

The work represents the results of researchers on the formation of composite fluoropolymer piezoelectric membranes based on a copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) and polyethylpyrrolidone (PVP) by the electrospinning method. The effect of the PVP content on the structure of the formed membranes was measured using scanning electron microscopy. The biocompatibility of the obtained membranes was studied by fluorescence microscopy on a model of human skin fibroblasts. The studied samples with a 0, 5 and 15% PVP content have good adhesive characteristics, preserve the viability and potential of cells to divide and therefore are most suitable for further use in regenerative medicine.

Effectiveness of Non-Woven Piezoelectric Polymer Membrane Application Based on a Co-Polymer of Vinylidene Fluoride with Tetrafluoroethylene for Oral Wound Closure

The aim of research is to study morphofunctional reorganization of the oral mucosa during regeneration of a wound defect using polymer membranes based on a copolymer of vinylidene fluoride with and without tetrafluoroethylene. Material and methods. The study included 35 white Wistar rats weighed 220–280 g. All animals were divided into three groups: group 1 – intact animals, group 2 – an experimental comparison group, and group 3 – an experimental main group. A wound defect in rats was formed by the excision of the mucosal flap in rats; this defect was overlapped by a polymer membrane in animals of the 3rd group. Histological and macroscopic studies were performed in 3, 7 and 12 days. Results. More rapid development of the granulated and loose fibrous connective tissue noted already on the 3rd day of the study was recorded in animals of the 3rd group. On the 7th day of the study a 1.5-time decrease in inflammatory infiltrate was recorded in animals of the experimental main group, while in the experimental comparison this indicator decreased in only 1.35 times. Moreover, the formation of the loose fibrous connective tissue in the main experimental group occurred 3.2 times more intensively than in the comparison group. On the 12th day, the specific area of the loose fibrous connective tissue in the experimental main group was 1.4 times larger, and the specific area of scar tissue was 3 times smaller than in the experimental comparison group. Conclusion. Application of polymer membrane demonstrated a decrease in inflammatory infiltrate and more rapid maturation of the loose fibrous connective tissue compared with the open wound management. Moreover, there was a significantly smaller formation of the dense fibrous connective tissue. Thus, it is possible to conclude on the effectiveness of polymer piezoelectric membrane application in the management of oral wound.

Characterizing photovoltaic backsheet adhesion degradation using the wedge and single cantilever beam tests, Part I: Field Modules

Photovoltaic backsheets are exposed to harsh outdoor weathering conditions throughout their service lives that can compromise their protective function, through adhesive debonding between their constituent layers and between the backsheet and the module. A large-scale study on adhesive degradation was conducted on 37 field-exposed modules, that spanned 19 different module manufacturers, that were deployed among six Köppen–Geiger climatic zones, and that were fielded between 0 and 28 years. Six outer layer polymer classes were identified among the backsheets: polyamide (PA), polyethylene terephthalate (PET), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), fluoroethylene vinyl ether copolymer (FEVE), and tetrafluoroethylene hexafluoropropylene vinylidene fluoride copolymer (THV). Two adhesion tests were used to measure the adhesive strength: the wedge test and the width-tapered single-cantilever beam (SCB) test. Adhesion energies were compared across exposure time and Köppen–Geiger climatic zone. Many of the PET-, PVF-, and PVDF-based backsheets experienced degradation of the adhesive layer between the backsheet outer and core layers. A consistent trend of decreasing adhesion energy with exposure time was observed in five out of the six backsheet types. Trends among adhesion energy and climatic zone, while expected, were not observed, possibly due to broad ranges in temperature, humidity, and precipitation defining Köppen–Geiger climatic zones. The cantilever beam measurements produced an upper cutoff of approximately 100 J/m2, above which no modules exhibited field delamination. The results are part of a two-part study quantifying adhesion in both field-weathered and indoor-exposed PV backsheets.

THE INVESTIGATION ON THERMAL OXIDATIVE DESTRUCTION AND ASSESSMENT OF RUBBER SERVICE PERIOD BASED ON TRIPLE COPOLYMER OF TETRAFLUOROETHYLENE, VINYLIDENE FLUORIDE AND HEXAFLUOROPROPYLENE

By thermogravimetric analysis it was studied the thermal oxidative degradation of rubber based on a triple copolymer of tetrafluoroethylene, vinylidene fluoride, and hexafluoropropylene. It was found that the object is characterized by a sufficiently high heat resistance, which is proven by the rather high temperature of loss of 5% of the initial mass of the sample (412 ° C). The service life of the tested unloaded material in air atmosphere, according to the Arrhenius equation, is 2084, 450 and 107 days at the temperature of 185, 200 and 215 ° C respectively.

Thin films of vinylidene fluoride copolymer with tetrafluoroethylene: dynamics of ferroelectric polarization switching

The vinylidene fluoride copolymer with tetrafluoroethylene P(VDF-TFE) is a typical ferroelectric polymer that has not been sufficiently studied so far in comparison with pure polyvinylidene fluoride (PVDF) and its copolymer with trifluoroethylene. The purpose of this work was to reveal the features of forming ferroelectric polarization and its switching in thin films of P(VDF-TFE) under various conditions, such as the level of the applied electric field and the duration of its action within 8 orders of magnitude from 10 μs to 100 s. The sequence of voltage pulses applied during poling and polarization reversal allowed to reveal the characteristics of the polarization switching dynamics. To increase the resolution of the measurements, two complementary methods of recording electrical induction were used. The features of polarization and space charge relaxation over time have been studied by thermally stimulated depolarization method. A new phenomenon of gradual separation of the relaxation processes associated with polarization and space charge was observed. Both components were accompanied by trapped charges that compensated the depolarizing field. Several practical recommendations have been formulated regarding the desirable values of poling parameters and additional processing to increase the ferroelectric polarization stability.

The synergistic effect of fluorosilicone and silica towards the compatibilization of silicone rubber and fluoroelastomer based high performance blend

Fluoroelastomer and silicone rubber lie in the two different poles of elastomer family in terms of polarity. Hence, combining them in a single material and making it as at least technologically compatible substance is a great challenge. In this article, the compatibilization effect of fluorosilicone rubber (block copolymer) (trifluoropropylpolydimethylsiloxane) with various loading of modified silica filler on the novel advanced polymer architecture based fluoroelastomer (copolymer of hexafluoropropylene, vinylidene fluoride, and tetrafluoroethylene) and silicone rubber (poly methylvinylsiloxane) blends has been studied in details. The mechanical properties show significant improvement at room temperature (13%) and remarkably more at high temperature (54%) for the compatibilized system. Tan delta peak shifting in DMA study indicates better compatibilization for 2.5 phr loading of fluorosilicone and 15 phr loading of silica at 50/50 blend ratio. The reduction in domain size (from ⁓3 μm to ⁓200 nm) of the fluorocarbon phase by the synergistic effect of silica and fluorosilicone proves the decrease in interfacial tension and better compatibilization. This blend can be judiciously applicable in the sealing system as oil and fuel resistant O-rings and gaskets for a very wide range of temperature.

Octa-viologen substituted polyhedral oligomeric silsesquioxane exhibiting outstanding electrochromic performances

• We synthesized octa-hexyl viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS). • Electrochromic devices were fabricated using OHV-POSS incorporated ion gel compositions. • The prepared device showed excellent electrochromic properties and switching stability. • Flexible electrochromic devices were fabricated on silver nanowire-PEDOT:PSS composite electrodes. • The fabricated device exhibited superb electrochromic performance with repeated bending cycles. We present a new strategy for improving the electrochromic properties of single-layered ion gels for electrochromic devices (ECDs) by incorporating octa-hexyl viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS). Newly synthesized OHV-POSS was included in ion gel compositions containing a poly(vinylidene fluoride) copolymer and ionic liquid to produce a freestanding film. When applied in single-layered ECDs, due to high ionic conductivity and fast charge transfer, the OHV-POSS film exhibited outstanding electrochromic performances with low redox potentials at −1.1 V, high transmittance changes (ΔT) of 56.1%, and a moderate coloration efficiency (CE) of 124.1 cm 2 /C. When combined with isooctyl polyhedral oligomeric silsesquioxane (IO-POSS), the device performances were remarkably enhanced, exhibiting a ΔT of 67.2% and CE of up to 307.8 cm 2 /C. In addition, the fabricated device maintained its switching stability for up to >12,000 cycles with a switching speed of 8.6 s. The electrochromic improvement is attributed to the presence of a POSS (Si-O-Si) cross-linkable cage structure featuring robust mechanical properties. In addition, flexible ECDs were fabricated on silver nanowire-PEDOT:PSS composite electrodes, and superb electrochromic performances were achieved with repeated bending cycles (>200 cycles). This study’s results present a promising tool for the material design of high-performance stable ECDs for long-term operation in displays, eyewear, and transmissive windows.

Composition Polymeric Membranes Based on the VDF-TeFE Copolymer Formed by Electrospinning

The paper presents the results of pilot studies on the formation of non-woven hydrophilic piezoelectric composite polymer membranes based on a copolymer of vinylidene fluoride and tetrafluoroethylene (VDF-TeFE) and polyethenylpyrrolidine (PEP) by electrospinning. Using optical goniometry, the effect of the PEP content on the wetting of the membrane surface with water was established. Using scanning electron microscopy, the influence of the content PEP on the structure of the formed membranes was studied. The effect of an isotonic NaCl solution on the structure of the formed membranes upon their dissolution within 7 days was studied. Based on studies of the chemical composition of the membranes before and after their dissolution, an assumption was made about the possibility of using the developed membranes for targeted delivery of pharmacological preparations for wound healing.

Magnetron plasma modification by sputtering copper target of electrospun fluoropolymer material to possess bacteriostatic properties

Abstract Polymer matrices from the copolymer of vinylidene fluoride with tetrafluoroethylene (VDF-TeFE) were successfully formed by the method of electrospinning. The matrices were successfully modified by DC magnetron sputtering of the copper target in the argon plasma discharge. To investigate the morphology and elemental composition of VDF-TeFE matrices, the following methods were used: scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), correspondingly. The results of SEM showed that polymer matrices consist of chaotically interlaced fibers whose diameters range from 0.2 to 1.4 μm. Using the EDX method, it was determined that as the modification time increases, the F/C ratio decreases, and the Cu/O increases. To study the wettability, the marginal angles were measured by the interaction of the surface with water. The wetting angle varies from 125.1° to 130.9°. Investigation of antibacterial properties has revealed that the polymeric matrix with modification time 120 s has bacteriostatic properties.

Electromagnetic interference shielding of carbon nanotube-fluoropolymer elastomer composites with layered structure

This paper presents carbon nanotubes-containing polymer composites with layered gradient structure having electromagnetic interference (EMI) shielding properties. Polymer composite films were obtained on metal surface by aerosol deposition of a dispersion of carbon nanotubes in the solution of a copolymer of vinylidene fluoride with hexafluoropropylene (SCF-26) in acetone. Single-wall TUBALL (OCSiAl) carbon nanotubes were used. Three-layer coatings were formed with a concentration of nanotubes decreasing in each subsequent deposited layer. The reflection coefficient of electromagnetic radiation in the range of 20–35 GHz was measured. Gradient samples had significantly better characteristics compared to samples with uniform concentration of carbon nanotubes: the reflection coefficient reached −6dB at 35 GHz. The outer layer of gradient structure with 0.1 wt % CNT provides a better matching of the wave resistance with free space and a smooth entrance of an electromagnetic wave into the sample. The subsequent layers with an increasing concentration of single-walled carbon nanotubes (0.3 and 0.5%) absorb electromagnetic radiation. Polymer elastomer composite EMI shielding coatings with concentration gradient can be applied by aerosol deposition to the surfaces of any composition and shape. Our results could serve as a design tool in carbon nanotubes - based EMI shielding flexible polymer coatings.

Piezoelectric polymer membranes with thin antibacterial coating for the regeneration of oral mucosa

Herein, we have fabricated non-woven piezoelectric polymer membranes from a copolymer of vinylidene fluoride with tetrafluoroethylene by electrospinning for the regeneration of oral mucosa. In endeavor to make the antibacterial membranes, we have deposited a thin copper coating on the outer surface of the material via magnetron sputtering. The study of the physicochemical properties of membranes over the course of various plasma treatment times demonstrated that while coating deposition does not affect material physico-chemical properties, it allows making the membranes antibacterial. In vivo studies have shown that non-woven piezoelectric polymer membranes contribute to the oral mucosa regeneration and the copper antibacterial coating accelerates this process largely.

Structural Evolution Mechanism of Crystalline Polymers in the Isothermal Melt-Crystallization Process: A Proposition Based on Simultaneous WAXD/SAXS/FTIR Measurements.

Time-resolved simultaneous measurements of wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) (and FTIR spectra) were performed for various kinds of crystalline polymers in isothermal melt-crystallization processes, from which the common features of the structural evolution process as well as the different behaviors intrinsic to the individual polymer species were extracted. The polymers targeted here were polyethylene, isotactic polypropylene, polyoxymethylene, aliphatic nylon, vinylidene fluoride copolymer, trans-polyisoprene, and poly(alkylene terephthalate). A universal concept of the microscopically viewed structural evolution process in isothermal crystallization may be described as follows: (i) the small domains composed of locally regular but more or less disordered helical chain segments are created in the melt (this important information was obtained by the IR spectral data analysis); (ii) these domains grow larger as the length and number of more regular helical segments increase with time; (iii) the correlation among the domains becomes stronger and they approach each other; and (iv) they merge into the stacked lamellar structure consisting of the regularly arranged crystalline lattices. The inner structure of the domains is different depending on the polymer species, as known from the IR spectral data.