Polyvinylidene fluoride

About: Polyvinylidene fluoride is a research topic. Over the lifetime, 7015 publications have been published within this topic receiving 98986 citations. The topic is also known as: Polyvinylidene difluoride & PVDF.

Enhanced microwave absorption property of reduced graphene oxide (RGO)-MnFe2O4 nanocomposites and polyvinylidene fluoride.

Abstract: MnFe2O4 nanoparticles have been synthesized on a large scale by a simple hydrothermal process in a wild condition, and the RGO/MnFe2O4 nanocomposites were also prepared under ultrasonic treatment based on the synthesized nanoparticles. The absorption properties of MnFe2O4/wax, RGO/MnFe2O4/wax and the RGO/MnFe2O4/PVDF (polyvinylidene fluoride) composites were studied; the results indicated that the RGO/MnFe2O4/PVDF composites show the most excellent wave absorption properties. The minimum reflection loss of RGO/MnFe2O4/PVDF composites with filler content of 5 wt % can reach −29.0 dB at 9.2 GHz, and the bandwidth of frequency less than −10 dB is from 8.00 to 12.88 GHz. The wave absorbing mechanism can be attributed to the dielectric loss, magnetic loss and the synergetic effect between RGO+MnFe2O4, RGO+PVDF and MnFe2O4+PVDF.

From vinylidene fluoride (VDF) to the applications of VDF-containing polymers and copolymers: recent developments and future trends.

Abstract: After an introduction reporting the properties and the applications of fluoropolymers, a first part deals with i) the main routes to produce vinylidene fluoride (VDF) monomer, ii) its homopolymerization, and iii) the advantages and uses of polyvinylidene fluoride (PVDF). In a second section, this review, illustrated by numerous examples, extensively reports the synthesis, properties and applications of the copolymers based on VDF with non-halogenated, fluorinated, commercially available or synthesized comonomers. These comonomers exhibit XYC=CZ-Sp-R structures where X, Y, and Z represent H, F, and CF3 groups, Sp a spacer and R a function such as OH, OAc, SAc, CO2R' (R' being a H atom or an alkyl group), CN, P(O)(OR')2 and SO3H. According to the nature and to the amount of the comonomer, the copolymers can be thermoplastic, elastomeric or thermoplastic elastomers. Introducing reactive R side groups brings complementary properties such as hydrophily, ionic exchange or surface properties, or further crosslinking of the resulting copolymers. Then, the kinetics of radical copolymerization of VDF with M comonomers led to the assessment of the reactivity ratios which are compared. Hence, a reactivity series of these M comonomers with respect to a macroradical terminated by VDF is proposed. Usually, these copolymers exhibit random structures but only three comonomers produced alternating copolymers with VDF: hexafluoroisobutylene, F2C=CFCO2CH3, and H2C=C(CF3)CO2R. The controlled radical copolymerizations of VDF with other comonomers (such as chlorotrifluoroethylene, 3,3,3-trifluoropropene, hexafluoropropylene, perfluoromethyl vinyl ether or-trifluoromethacrylic acid) either in the presence of xanthates, borinates or iodo-compounds are also reported. In addition, new VDF-containing copolymers exhibit well-defined architectures, such as block and graft copolymers. They can be synthesized either by conventional techniques or by controlled radical copolymerization. Chemical modifications of PVDF and poly(VDF-co-monomer) copolymers are also presented. Several properties and applications (such as surfactants, dielectrical polymers, thermoplastic elastomers, fuel cell and ultrafiltration membranes, or polycondensates, the fluorinated segments of which bringing softness and thermal stability) of these VDF-containing copolymers will illustrate this review.

Effect of nano sized al2o3-particle addition on pvdf ultrafiltration membrane performance

Abstract: A polyvinylidene fluoride (PVDF) ultrafiltration (UF) membrane was modified by dispersing nano-sized alumina (Al2O3) particles uniformly in a PVDF solution (19% polymer weight). Membranes were prepared by a phase-inversion process and using UF experiments comparing water flux and, molecular-weight cut-offs for the wet membranes. The contact angle between water and the membrane surface was measured in order to quantify the hydrophilicity changes of the membrane surface. Membranes surface morphology, surface and cross-sectional structures, and nanometer-particle distribution on the membrane surface were examined by atomic-force microscopy (AFM), scanning electron microscopy (SEM), and confocal laser-scanning microscopy (CLSM), respectively. Thermal analysis (DSC) was performed in order to investigate the interactions between membrane components. The effects of the nanometer Al2O3-particles concentration in the polymer dope on the permeation properties, membrane strength, and anti-fouling performance were examined. The experimental results indicated that Al2O3–PVDF composite membranes exhibit significant differences in surface properties and intrinsic properties due to nanometer-particles addition.

History and recent progress in piezoelectric polymers

Abstract: Electrets of carnauba wax and resin have exhibited good stability of trapped charges for nearly 50 years. Dipolar orientation and trapped charge are two mechanisms contributing to the pyro-, piezo-, and ferroelectricity of polymers. Since the 1950s, shear piezoelectricity was investigated in polymers of biological origin (such as cellulose and collagen) as well as synthetic optically active polymers (such as polyamides and polylactic acids). Since the discovery of piezoelectricity in poled polyvinylidene fluoride (PVDF) in 1969, the pyro-, piezo-, and ferroelectricity were widely investigated in a number of polar polymers, such as copolymers of vinylidene fluoride and trifluoroethylene, copolymers of vinylcyanide and vinylacetate, and nylons. Recent studies involve submicron films of aromatic and aliphatic polyureas prepared by vapor deposition polymerization in vacuum and the piezoelectricity of polyurethane produced by the coupling of electrostriction and bias electric fields. Gramophone pickups using a piece of bone or tendon were demonstrated in 1959. Microphones using a stretched film of polymethyl glutamate were reported in 1968. Ultrasonic transducers using elongated and poled films of PVDF were demonstrated in 1972. Headphones and tweeters using PVDF were marketed in 1975. Hydrophones and various electromechanical devices utilizing PVDP and its copolymers have been developed during the past 30 years. This paper briefly reviews the history and recent progress in piezoelectric polymers.

Preparation and characterization of PVDF-SiO2 composite hollow fiber UF membrane by sol-gel method

Abstract: Organic–inorganic polyvinylidene fluoride (PVDF)–silica (SiO2) composite hollow fiber ultrafiltration (UF) membranes were prepared by the combination of a tetraethoxysilane (TEOS) sol–gel process with a wet-spinning method. The membrane formation mechanisms were investigated in terms of viscosity, precipitation kinetics and morphology. Results showed the dope viscosity increased with the increment of TEOS concentration in dope. The addition of TEOS accelerated the precipitation of the dope. SEM pictures showed the cross-section morphology of PVDF composite membranes changed from finger-like macrovoids to sponge-like structure with increasing SiO2 content. The mechanical, thermal stabilities and permeation property of PVDF–SiO2 composite membranes were further examined. At lower TEOS concentration, the hydrolyzed SiO2 particles, which were homogeneously dispersed in PVDF matrix, acted as the physical crosslinking points, and led to an improvement of mechanical and thermal properties. While at higher TEOS concentration, SiO2 formed network, which restricted the movement of PVDF and led to the decrease of the mechanical and thermal stabilities. Moreover, XRD and FTIR results revealed that the crystal structure of PVDF underwent a transition from α-phase to β-phase due to the addition of TEOS. The contact angle and UF experimental results of PVDF–SiO2 composite membranes showed an improvement of hydrophilicity and permeability. The PVDF–SiO2 membrane prepared from the dope with 3 wt.% TEOS concentration had the best UF performance and antifouling property.