Hexafluoropropylene Copolymer Research Articles

A Low‐Permeability and Flexible Polymer Tube for Long‐Life Fiber Lithium‐Ion Batteries

AbstractFiber lithium‐ion batteries (FLIBs) hold great promise for powering wearable electronics. However, their practical application is hindered by limited cycle and calendar life, primarily due to the loss of active Li caused by water vapor permeation through the encapsulation layer. To address this challenge, a low‐permeability and high‐flexibility tetrafluoroethylene hexafluoropropylene copolymer (FEP) tube is presented to continuously encapsulate FLIBs by melting extrusion method. Owing to the inherent hydrophobicity of fluorine resins and appropriate crystallinity of the polymer matrix, FEP tubes exhibited significantly low vapor permeability, with a water vapor transmittance rate (WVTR) of 0.3 mg·day−1·pkg−1, 15 times lower than that of the nylon 12 tubes (4.6 mg·day−1·pkg−1). Leveraging the low permeability and elastic modulus of FEP tubes, FLIBs demonstrate a capacity retention of 80.05% after 180 cycles and exceptional flexibility with a capacity retention of 98.32% after 10 000 bending cycles, showcasing superior performance compared to the conventional polymer tubes (for example, the capacity of PP‐FLIBs declined by 20.68% after 30 cycles). This work presents a general and efficient strategy for continuously encapsulating FLIBs, effectively extending their cycle and calendar lifetime of FLIBs, thereby enhancing their practical viability for wearable electronic applications.

Synthesis and Properties of Polyvinylidene Fluoride-Hexafluoropropylene Copolymer/Li6PS5Cl Gel Composite Electrolyte for Lithium Solid-State Batteries.

Gel electrolytes for lithium-ion batteries continue to replace the organic liquid electrolytes in conventional batteries due to their advantages of being less prone to leakage and non-explosive and possessing a high modulus of elasticity. However, the development of gel electrolytes has been hindered by their generally low ionic conductivity at room temperature and high interfacial impedance with electrodes. In this paper, a poly (vinylidene fluoride)-hexafluoropropylene copolymer (PVdF-HFP) with a flexible structure, Li6PS5Cl (LPSCl) powder of the sulfur-silver-germanium ore type, and lithium perchlorate salt (LiClO4) were prepared into sulfide gel composite electrolyte films (GCEs) via a thermosetting process. The experimental results showed that the gel composite electrolyte with 1% LPSCl in the PVdF-HFP matrix exhibited an ionic conductivity as high as 1.27 × 10-3 S·cm-1 at 25 °C and a lithium ion transference number of 0.63. The assembled LiFePO4||GCEs||Li batteries have excellent rate (130 mAh·g-1 at 1 C and 54 mAh·g-1 at 5 C) and cycling (capacity retention was 93% after 100 cycles at 0.1 C and 80% after 150 cycles at 0.2 C) performance. This work provides new methods and strategies for the design and fabrication of solid-state batteries with high ionic conductivity and high specific energy.

High-Performance All-Textile Triboelectric Nanogenerator toward Intelligent Sports Sensing and Biomechanical Energy Harvesting.

Merging textiles with advanced energy harvesting technology via triboelectric effects brings novel insights into self-powered wearable textile electronics. However, fabrication of a comfortable textile-based triboelectric nanogenerator (TENG) with high outputs remains challenging. Herein, we propose a highly flexible, tailorable, single-electrode all-textile TENG (t-TENG) with both wear comfort and high outputs. A dielectric modulated porous composite coating containing poly(vinylidene fluoride)-hexafluoropropylene copolymer and barium titanate nanoparticles is constructed on conductive fabric to counterpart with highly positive glass fiber fabric through knotted yarn bonding, maintaining the superiority of textiles and strong triboelectricity. Through the synergistic optimization of charge storage via dielectric modulation and charge dissipation offset by electrical poling, remarkable outputs (261 V, 1.5 μA, and 12.7 nC) are obtained from a miniaturized, lightweight t-TENG (2 × 2 cm2, 130 mg) with an instantaneous power density of 654.48 mW·m-2, as well as excellent electrical robustness and device durability over 20,000 cycles. The t-TENG also exhibits a high sensitivity of 3.438 V·kPa-1 in the force region (1-10 N), demonstrating great potential in TENG-based intelligent sports sensing applications for monitoring and correcting the basketball shooting hand and foot arch posture. Furthermore, over 110 light-emitting diode arrays can be lightened up by gently tapping this miniaturized t-TENG. It also offers a wearable power source scheme through integrating the single-electrode device into clothing and utilizing the skin as the grounded electrode, revealing its ease of integration and biomechanical energy harvesting capability. This work provides an attractive paradigm for next-generation textile electronics with well-balanced device performance and wear comfort.

Designing a multi-stage MoS2 fiber membrane for photothermal membrane distillation

Among the various desalination technologies, membrane distillation (MD) stands out for its high salt rejection, low operating temperature and operating pressure. Photothermal membrane distillation (PMD) represents an innovative approach to membrane distillation (MD), wherein the process harnesses plentiful and renewable solar energy to achieve localized heating at the interface between the membrane and the feed solution. This is achieved by employing photothermal materials, eliminating the need for heating a substantial volume of the feed solution. This study has prepared membranes with micro/nano fiber interwoven structure based on polystyrene (PS) and polyvinylidene fluoride hexafluoropropylene copolymer (PVDF-HFP) by electrospinning technology, and constructed multi-stage MoS2 photothermal fiber membranes by hydrothermal growth process. The PS/PVDF-HFP micro/nano fiber membrane possesses a spacious pore structure and high porosity, serving as a robust framework that facilitates swift transport of water vapor. The MoS2 nanoflowers uniformly grown on the micro/nano fibers have both metal 1T and semiconductor 2H phases, which facilitate the absorption of sunlight, reaching an average absorbance of 90.9 % in the240-2600 nm wavelength range. Under 1 kW m−2 solar illumination, the surface temperature of the PS/PVDF-HFP/MoS2 membrane could be raised to 74.2 °C after 120 s. The permeate flux was stable at 1.21 ± 0.02 L m−2 h−1 within 20 h PMD. The membrane showcased a salt rejection rate of 99.96 % and achieved an energy efficiency of 72.08 %. This suggests that the multi-stage MoS2 photothermal fiber membrane, characterized by remarkable stability and high photothermal conversion efficiency, lays a solid foundation for advancing research in the field of PMD applications.

Influence of physical aging of ferroelectric vinylidene fluoride copolymer films on their structural and electrophysical characteristics

AbstractGeneral problems of structural changes which occur at storage of two‐phase crystalline polymers with a metastable structure at room conditions are considered on the example of a vinylidene fluoride ‐ hexafluoropropylene copolymer. The physical aging occurs in flexible‐chain crystalline polymers (polyethylene, fluoropolymers under consideration, etc.), where, due to low glass transition temperatures, the liquid‐like dynamics of amorphous phase chains is realized at room temperature through cooperative micro‐Brownian motions with short relaxation times. Taking into account that covalent‐bound sections of the chains of the amorphous phase can enter the crystallites, the noted mobility may initiate changes in the size of the latter. Such a possibility is proved by the example of the noted copolymer. At low‐temperature crystallization of a vinylidene fluoride ‐ hexafluoropropylene copolymer from a solution the formed α‐phase crystals have little perfection. The size of the crystals increases when the films are stored in room conditions. Because of the crystal polymorphism, at the same time a certain fraction of γ‐phase crystals which are present in initial films undergo a polymorphic transformation γ → α. These processes lead to an increase in crystallinity. Moreover, during such processes additional structuring is observed, which is reduced to the displacement of various kinds of intra‐chain defects into the amorphous phase (and especially into the surface). Since the copolymers under study are ferroelectrics, they were studied by piezo force microscopy. It was found that despite the crystallization predominantly in nonpolar α‐phase, piezo force microscopy revealed a domain structure, which formation mechanism is discussed. The structural changes at physical aging of the films affect the character of the noted domain structure. Thus, it is suggested that the mechanism of the described structural changes is realized through the developed cooperative mobility of the chains in the amorphous phase, which characterizes the processes of rotational diffusion.

Ultra-low friction, superhydrophobic, plasma micro-nanotextured fluorinated ethylene propylene (FEP) surfaces

Fluorine-containing polymers have attracted a lot of interest due to their hydrophobic nature, which enables a number of functionalities such as low friction, self-cleaning, anti-sticking, etc. Fluorinated ethylene propylene (FEP) is a copolymer of hexafluoropropylene and tetrafluoroethylene. In contrast to polytetrafluoroethylene (PTFE), FEP is melt-processable using injection molding and it is highly transparent and resistant to sunlight. Here, we transform fluorinated ethylene propylene ( FEP) surfaces to superhydrophobic using plasma processing (i.e. plasma etching with simultaneous micro-nanotexturing followed by plasma deposition). Two different plasma reactors (an inductively coupled reactor and a reactive ion etcher) and different etching conditions are used in order to micro-nanotexture FEP surfaces. Superhydrophobicity is achieved after plasma deposition of a thin (30 nm) fluorocarbon coating. Subsequently, we probe their frictional properties against water drops using a tilting stage. In particular, we demonstrate wetting control of FEP surfaces with water static water contact angle ranging from 95 o to 168 o and hysteresis down to 1–2 o . Video analysis of drops moving on different FEP surfaces shows that water drops exhibit reduced friction as etching time increases so that a hierarchical morphology is created. This is achieved using both plasma reactors, whereas the optimum performance is observed for the 10 min etched surface in a inductively coupled plasma reactor in which friction force becomes 0.7–1 μN, which corresponds to an ultra-low dynamic coefficient of friction (at least one order of magnitude lower to that of untreated FEP). • Plasma Processing for wetting control of FEP surfaces. • Superhydrophobic FEP surfaces are demonstrated. • Water drops move with reduced friction on SH FEP surfaces. • Coefficient of friction is reduced to 0.007 for SH FEP surfaces.

Optimization of cathode microporous layer materials for proton exchange membrane fuel cell

The microporous layer (MPL) of diffusion medium has an important impact on the water management ability of proton exchange membrane fuel cells. In this study, six kinds of carbon black were used to prepare the cathode MPL. The thickness, conductivity, pore structure, hydrophobicity, and surface microstructure of MPL were characterized. The single cell was prepared and electrochemical tests were performed. The results showed that the single cell prepared by Acetylene black (ACET) and Vulcan XC-72R has a considerable power generation performance. In addition, polyvinylidene fluoride hexafluoropropylene copolymer P(VDF-HFP) was used to replace Polytetrafluoroethylene (PTFE) as hydrophobic binder. MPL with different P(VDF-HFP) contents were prepared, and the single cell performance was investigated. The results showed that all the single cells prepared by P(VDF-HFP) were worse than that of PTFE. This study provides an important reference for further improving the performance of fuel cells from the perspective of material optimization with MPL.

Полиэлектролитный герметик для топливных элементов на основе привитых фторсополимеров

The preparation of grafted copolymers for electrochemical devices by chemical grafting copolymerization of acrylic acid and α-, β-, β-trifluorostyrene to a film fluorinated copolymer of hexafluoropropylene with vinylidene fluoride is described. The grafted copolymers contained carboxyl groups and the sulfonation process was carried out for additional introduction of ionic sulfo- groups. The optimal conditions for the process have been determined, which make possible to obtain grafted copolymers with a wide range of electrochemical and physical-mechanical properties. The resulting products in the form of ion-conducting membranes can be used as part of current sources and other electrochemical devices and have a specific volumetric electrical resistance of 0.46—1.41 Ohm.m, exchange capacity 1.45—1.62 meq / g, moisture content 25—62%, breaking stress 0.82—1.08 MPa.

Gel-polymer electrolytes plasticized with pyrrolidinium-based ionanofluid for lithium battery applications

In the present study, hexafluoropropylene copolymer (P(VDF-HFP))-based “active” polymer membranes are prepared by entrapping different extent of pyrrolidinium ionic liquid-based nanofluid (ionanofluid). X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) spectroscopy are implemented to characterize the membranes. The study reveals that ionanofluid improves the electroactive phase nucleation of P(VDF-HFP) and suppresses the membranes’ crystallinity. SEM micrographs and butanol absorption study indicate that ionanofluid improves the electrolyte uptake ability and facilitates forming unified ion-conducting channels within the membranes. The 50 wt% ionanofluid (INF) incorporated gel-polymer electrolyte (GPE) exhibits the highest room-temperature ionic conductivity (2.33 × 10−3 S cm−1 at 25 °C), a high lithium-ion transference number ( $$ {t}_{{\mathrm{Li}}^{+}}\sim 0.6 $$ ), superior electrochemical stability window up to ~ 5.3 V (vs. Li/Li+) and excellent interfacial compatibility with the lithium electrode. The LiFePO4/Li battery comprising INF-based GPE demonstrates good C-rate performance and excellent cycling stability with a discharge capacity of ~ 156 mAh g−1 and ~ 116 mAh g−1 at C/5 and 2 C rates, respectively, and capacity retention of > 95% after 50 cycles at C/5 rate.

Ionic liquid-based novel polymer electrolytes: electrical and thermal properties

New polymer electrolytes have been prepared from room temperature ionic liquid (IL) and poly(vinylidene fluoride)-hexafluoropropylene copolymer [PVdF-HFP]. The variation of thermal and electrical properties with varying polymer to IL concentration was investigated. The electrolytes had high thermal stabilities. The IL-PVdF-HFP electrolytes were freestanding, flexible films with room temperature conductivities of the order of 10−3 S cm−1. Increase in conductivity was found with increasing IL and also with increasing temperature. Increase in conductivity can be attributed to the fact that with increasing IL amorphicity increases as evident from XRD result. Dielectric studies showed decrease in relaxation time with increasing IL concentration indicating increase in polymer segmental motion which result in increase in conductivity.

Proteolytically Degraded Alginate Hydrogels and Hydrophobic Microbioreactors for Porcine Oocyte Encapsulation.

In reproductive biology, the biotechnology revolution that began with artificial insemination and embryo transfer technology led to the development of assisted reproduction techniques such as oocyte in vitro maturation (IVM), in vitro fertilization (IVF) and cloning of domestic animals by nuclear transfer from somatic cell. IVM is the method particularly of significance. It is the platform technology for the supply of mature, good quality oocytes for applications such as reduction of the generation interval in commercially important or endangered species, research concerning in vitro human reproduction, and production of transgenic animals for cell therapies. The term oocyte quality includes its competence to complete maturation, be fertilized, thereby resulting in healthy offspring. This means that oocytes of good quality are paramount for successful fertilization including IVF procedures. This poses many difficulties to develop a reliable culture method that would support growth not only of human oocytes but also of other large mammalian species. The first step in IVM is the in vitro culture of oocytes. This work describes two protocols for the 3D culture of porcine oocytes. In the first, 3D model cumulus-oocyte complexes (COCs) are encapsulated in a fibrin-alginate bead interpenetrating network, in which a mixture of fibrin and alginate are gelled simultaneously. In the second one, COCs are suspended in a drop of medium and encapsulated with fluorinated ethylene propylene (FEP; a copolymer of hexafluoropropylene and tetrafluoroethylene) powder particles to form microbioreactors defined as Liquid Marbles (LM). Both 3D systems maintain the gaseous in vitro culture environment. They also maintain COCs 3D organization by preventing their flattening and consequent disruption of gap junctions, thereby preserving the functional relationship between the oocyte, and surrounding follicular cells.

Shock initiation of the HMX-based explosive PBX 9012: Experiments, uncertainty analysis, and unreacted equation-of-state

Shock initiation experiments have been carried out on the polymer-bonded explosive PBX 9012 [nominally 90% octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX), 10% vinylidene–hexafluoropropylene copolymer (Viton A) by weight] in order to provide calibration data for the explosive’s unreacted equation-of-state (EOS) and shock-to-detonation transition for reactive burn rate calibration. The input pressures covered the range of 1.86–4.43 GPa. This provided run-to-detonation depths ranging from >22.3mm for the lowest pressure shot to 4.91 mm at the highest pressure. The relative shock sensitivity of PBX 9012 is compared to other HMX-explosives in terms of the Pop-plot, showing that the studied explosive is more sensitive than other similar HMX-based counterparts (with notable exceptions). The uncertainty in the shock velocity determinations from the shock tracker measurements are also investigated, yielding new uncertainty measures in the generated Hugoniot data and run-to-detonation coordinates. Finally, the unreacted equation-of-state is determined using a linear Us–up Mie–Grüneisen relation and the Davis reactants EOS analytical form, the latter being more suited for reactive burn modeling.

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.

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.

Исследование высокотемпературного предела текучести армированного углерод-ными волокнами сополимера тетрафторэтилена с гексафторпропиленом

Исследование высокотемпературного предела текучести армированного углерод-ными волокнами сополимера тетрафторэтилена с гексафторпропиленом

Application of piezoelectric electrets to an energy-harvesting system

We developed a prototype system with a simple structure for energy-harvesting as humans walk in their daily life, using piezoelectric electrets as piezoelectric-power-generating elements. We prepared a porous poly(tetrafluoroethylene) (p-PTFE) film with a thickness of 12 μm and an average pore size of 0.7 μm sandwiched by two films of tetrafluoroethylene–hexafluoropropylene copolymer (FEP) with a thickness of 6 μm (FEP/p-PTFE/FEP film) as an electret film used for the energy-harvesting device. A corona discharge system used to fabricate an FEP/p-PTFE/FEP film with an area of 20 × 20 cm2 that generates piezoelectricity (electret FEP/p-PTFE/FEP film). The electret FEP/p-PTFE/FEP film had a piezoelectric constant d33 of more than 100 pC/N. Then, we fabricated a multilayer film by stacking the metal foil and the electret FEP/p-PTFE/FEP film without forming wrinkles or streaks. The voltage, current, and power generated by the electret FEP/p-PTFE/FEP multilayer film during an exercise involving a research subject repeatedly stepping on the film placed in the floor were evaluated. The maximum instantaneous generated power was about 4500 μW each time the subject stamped up and down. The energy consumed in transmitting an 8-byte signal using a Bluetooth Low Energy (BLE) device is known to be about 600 μW. Considering the electricity consumption of BLE devices, the above result strongly indicates that the power generated by the electret FEP/p-PTFE/FEP multilayer film has great potential for use in BLE devices.

Fabrication of Matrices of Nonwoven Porcine Carotid Arteries and Investigation of their Functional Properties

The process of molding tubular matrices of porcine carotid arteries by electroforming from polycaprolactone and a mixture of F-26 fluoroplastic with SKF-26 synthetic fluorine-containing rubber (SFR), which is a vinylidene fluoride−hexafluoropropylene copolymer, is studied. The mechanical properties of the formed matrices in dry and wet state are studied and they are compared with native vessels, the composition of the matrix material is optimized, the molding conditions are set, and the desired vessel wall thickness is chosen. It is shown that the matrices fabricated from fluoroplastics are akin to native vessels in functional properties.

A Novel Shape-Memory Monofilament Suture for Minimally Invasive Thoracoscopic Cardiac Surgery.

Endoscopic knot tying can complicate or prolong minimally invasive surgical procedures. A novel shape-memory monofilament suture with a spiral tail has been developed to speed up suture fixation during minimally invasive cardiac surgery. The purpose of this study was to evaluate its usefulness and safety in minimally invasive cardiac surgery. We installed a needle with a 4-0 monofilament suture, composed of polyvinylidene difluoride and hexafluoropropylene copolymers, in an originally invented jig and heated it in an oven. By only passing through the needle and then into the spiral made at the tail of the suture, a hangman's knot was easily made. For the fundamental experiment, to evaluate the effectiveness of the novel shape-memory monofilament suture, 4 surgeons with varying thoracoscopic experience tied knots within a simulated minimally invasive setting, using both the novel shape-memory and conventional monofilament sutures. The time elapsed for knot tying and tensile strength of each knot was measured. The mean knot-tying time was significantly shorter with the novel suture than with the conventional suture (108 ± 29 vs. 172 ± 42 seconds, P = 0.01). The ultimate tensile strength of each knot was 17.4 N in the novel suture and 16.5 N in the conventional suture. The novel shape-memory monofilament suture has great potential for reducing operative time of minimally invasive thoracoscopic surgery while retaining the strength of the knot.

The Selection of Plasticizer for Creating Oil-Filled Composites of Tribotechnical Designation Based on Aromatic Polyamide Phenylone C-2

It is proposed to use oil-filled polymers, so-called «oilyanites» for units and parts of tribotechnical designation based on polymer matrices. Materials of the given class can generally be considered as a three-component system consisting of a polymer binder, a plasticizer and multifunctional additives-fillers. Common to these materials is the «self-lubrication» effect, stemmed from the polymer plasticization. The aromatic polyamide Phenylone C-2 was used as the composite matrix. F4MB polytetrafluoroethylene powder (tetrafluoroethylene and hexafluoropropylene copolymer) and MgAl2O4 spinel nano additive were used as nanodimensional fillers and additives respectively. PMPS (polymethylphenylsiloxane), cylinder oil C-52, and VGO (vacuum gasoil) were used as a plasticizer, increasing the elasticity and plasticity of the material during processing and operation. The selection of the given oils and technical liquids is due to their ability to maintain their lubricating properties in high-temperature operating conditions, as the molding temperature of Phenylone samples is 300-320°C. The paper includes the comparative studies of physical, mechanical and tribological properties of oil-filled antifriction self-lubricating polymer composites carried out to assess the effect of the selected plasticizer.

Study of Coatings Derived from the Copolymer of Vinylidene Fluoride and Hexafluoropropylene

A study has been carried out on the swelling of a copolymer of vinylidene fluoride and hexafluoropropylene in organic solvents. The optimal conditions for dissolving this fluoroelastomer were determined. Vulcanization of the fluorocopolymer was carried out using amine hardeners, namely, m-xylylenediamine and 3-aminopropyltriethoxysilane. A mechanism was proposed for the hardening of the copolymer. The effects of these hardeners on the coating properties were compared.