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Patent

Non-Porous Polyvinylidene Fluoride (Pvdf) Films in the Beta Phase and Processing Method Thereof

TL;DR: In this paper, a new film of the beta phase of polyvinylidene fluoride (PVDF) and its processing for the elimination of porosity, using a compression force along the thickness direction of the sample at a high temperature.
Abstract: The invention reports a new film of the beta phase of polyvinylidene fluoride (PVDF) and its processing for the elimination of porosity, using a compression force along the thickness direction of the sample at a high temperature. The join action of the compression force and the temperature eliminates the porosity of the PVDF beta phase, improving its mechanical (Young's modulus, yielding and breaking stress, yielding and breaking strain), electrical (dielectric constant, electric rupture) and electromechanical properties (electromechanical coupling, piezoelectric coefficients) and, therefore, the use of the material in technological applications. Non-porous material, 95 to 100% in beta phase and with crystallinity degrees higher than 50%, is obtained.
Citations
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Proceedings ArticleDOI
04 Jul 2010
TL;DR: In this article, the authors describe the concept, design, fabrication and experimental results of a touchscreen based on acoustic pulse recognition, which uses piezoelectric transducers fabricated from PVDF in its beta phase.
Abstract: This article describes the concept, design, fabrication and experimental results of a touchscreen based on acoustic pulse recognition. It uses piezoelectric transducers fabricated from the piezoelectric polymer poly(vinylidene fluoride), PVDF, in its beta phase. The transducers are located at the edges of the panel in order to receive the acoustic pulses generated by the touches. Each transducer is connected to a readout electronic circuit composed by a differential charge amplifier and a comparator, whose output signal is attached to a microcontroller. The microcontroller uses an algorithm to determine the location of the touch, based on the time differences of the transducer signals. The touchscreen itself is made of ordinary glass, providing good durability and optical transparency. The experimental results obtained with the first prototype demonstrate the effectiveness of the method.

17 citations

Patent
28 Jan 2013
TL;DR: In this paper, the authors provided a piezoelectric element, including a porous fluororesin film made of a first fluororensin and a nonporous fluororesins layer stacked on at least one surface of the porous film.
Abstract: There is provided a piezoelectric element, including: a porous fluororesin film made of a first fluororesin; and a nonporous fluororesin layer stacked on at least one surface of the porous fluororesin film and made of a second fluororesin, wherein the first fluororesin is different in type from the second fluororesin, and when 50 pores are selected in descending order from a pore having the longest thickness-direction length, of pores present in a cut surface of the porous fluororesin film in a thickness direction, an average value A 50 of thickness-direction lengths of the 50 pores is 3 μm or smaller.

9 citations

Proceedings ArticleDOI
04 Jul 2010
TL;DR: In this paper, an acoustic microagitator for biological fluids analysis is described, where a piezoelectric transducer is used to heat the samples, improving the reaction of fluids that benefit from that effect.
Abstract: This article describes an acoustic microagitator for being used in biological fluids analysis. It is known that a piezoelectric transducer, with its vibration, can be used for mixing fluids. However, in this case, the piezoelectric transducer is also used to heat the samples, improving the reaction of fluids that benefit from that effect. The piezoelectric transducer is fabricated from a poly(vinylidene fluoride) polymer, in the beta phase (β-PVDF). This concept is demonstrated theoretically and by measuring the temperature profile in a regular 1 cm optical lightpath glass cuvette, using capillary thermocouples. This system can further be included in a lab-on-a-chip device, acting as a microreactor, for clinical diagnosis.

6 citations

Dissertation
01 Aug 2015
TL;DR: In this paper, both modified thermally induced method and modified plasma induced method are employed to oxidise PVDF polymer for its copolymerisation with NIPAAM monomers.
Abstract: The liquid chemical permeation properties and water vapour transmission properties of temperature sensitive poly(vinylidene fluoride) (PVDF) grafted N-isopropylacrylamide (NIPAAM) (NIPAAM-g-PVDF) copolymer membranes as a smart barrier layer in chemical protective clothing are studied in this research. Both modified thermally induced method and modified plasma induced method are employed to oxidise PVDF polymer for its copolymerisation with NIPAAM monomers. In the thermal induced method, NIPAAM-g-PVDF polymer materials are synthesised via the copolymerisation of ozone activated PVDF polymer with NIPAAM monomers below a lower critical solution temperature of NIPAAM (30°C). An effective supercritical carbon dioxide drying method is used as an alternative drying method to remove the solvent from the ozone activated PVDF polymer in conventionally copolymerisation is successfully applied and a new direct copolymerisation route by adding NIPAAM polymer into ozone activated PVDF in solutions without the drying process of the activated PVDF polymers. The NIPAAM-g-PVDF made by the new copolymerisation process is much simpler than the conventional method and the processing time needed is much shorter. In the oxygen plasma induced copolymerisation method, the porous PVDF membranes produced from the phase inversion method are treated oxygen plasma before they were copolymerised with NIPAAM monomer in N,N-dimethylformamide (DMF) solvent aqueous solution below the lower critical solution temperature of NIPAAM (30°C). The structural characteristics of heat-pressed NIPAAM-g-PVDF nanoporous membranes produced from the above two methods are investigated. The influence of the microstructure of the nanoporous copolymer membranes on both their water vapour transfer properties and dynamic permeation rate has been studied. The mechanisms of liquid/vapour permeation through the thermal sensitive copolymer nanoporous membranes are analysed and investigated. In this study, it is found that the breakthrough time and permeation rate of nanoporous NIPAAM-g-PVDF membranes are influenced by the proportion of NIPAAM components, the membrane thickness, the crystallinity and the porous structure of the NIPAAM-g-PVDF membranes. It is also found that the water vapour permeability of the heat-pressed NIPAAM-g-PVDF membranes at both 20°C and 40°C are influenced by the membrane thickness, the total pore volume and the porosity of the membranes. The water vapour permeability coefficient of the NIPAAM-g-PVDF nanoporous membranes is determined by both the proportion of thermal sensitive NIPAAM components and associated porous structure of the copolymer membranes.

5 citations

Patent
11 May 2016
TL;DR: In this paper, a texture piezoelectric polymer film of high transverse effect and a preparation method of the film is presented. But the texture is not textured.
Abstract: The invention discloses a texture piezoelectric polymer film of high transverse effect and a preparation method of the film. The nonisothermal crystallisation process of the film prepared by the solution method is controlled to realize preferable orientation of molecular dipole moment of the film is realized, and the piezoelectric polymer film of the texture structure in which the molecular dipoles are arranged preferably along the plane of the film is prepared. The piezoelectric polymer film is characterized in that the horizontal piezoelectric effect of the film is higher than that of a film of the same components but without texturizing, can be applied to preparation of a sensor of high transverse piezoelectric effect, and has good application prospects in the fields of a flexible nano generation system and a novel energy collection system.

2 citations

References
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Patent
16 Dec 1996
TL;DR: In this paper, a method of depositing a material onto a substrate comprises the steps of feeding a material solution comprising one or more precursor compounds, a solvent and a pH-modifying catalyst to an outlet to provide a stream of droplets of the material solution; generating an electric field to electrostatically attract the droplets from the outlet towards the substrate; and providing an increase in temperature between the outlet and the substrate.
Abstract: A method of depositing a material onto a substrate comprises the steps of: (a) feeding a material solution comprising one or more precursor compounds, a solvent and a pH-modifying catalyst to an outlet to provide a stream of droplets of the material solution; (b) generating an electric field to electrostatically attract the droplets from the outlet towards the substrate; and (c) providing an increase in temperature between the outlet and the substrate.

79 citations

Patent
06 Jul 2004
TL;DR: In this paper, the shape of a microporous article is produced from polyvinylidene fluoride and nucleating agents using thermally induced phase separation (TIPS) processes.
Abstract: Shaped microporous articles are produced from polyvinylidene fluoride (PVDF) and nucleating agents using thermally induced phase separation (TIPS) processes. The shaped microporous article is oriented in at least one direction at a stretch ratio of at least approximately 1.1 to 1.0. The shaped article may also comprise a diluent, glyceryl triacetate. The shaped microporous article may also have the micropores filled with a sufficient quantity of ion conducting electrolyte to allow the membrane to function as an ion conductive membrane. The method of making a microporous article comprises the steps of melt blending polyvinylidene fluoride, nucleating agent and glyceryl triacetate; forming a shaped article of the mixture; cooling the shaped article to cause crystallization of the polyvinylidene fluoride and phase separation of the polyvinylidene fluoride and glyceryl triacetate; and stretching the shaped article in at least one direction at a stretch ratio of at least approximately 1.1 to 1.0.

58 citations

Patent
18 Mar 1996
TL;DR: In this paper, the microporous polyvinylidene fluoride (PVDF) membranes were made from vinylidene fluoride polymers and the products produced. And they have unique macrostructural features responsible, in part, for their unique functional properties.
Abstract: Methods for making microporous polyvinylidene fluoride (PVDF) membranes from vinylidene fluoride polymers and the products produced. The PVDF microporous membranes have a significantly faster flow rate at a given pore size as compared to equally-sized microporous membranes made by conventional procedures. The PVDF microporous membranes also have significantly smaller pore sizes than conventional microporous PVDF membranes. The present membranes have unique macrostructural features responsible, in part, for their unique functional properties. The process includes dissolving the polymer in a liquid that includes a solvent and a co-solvent for the polymer. The dissolution of the polymer can be at temperatures ranging from about 20° C. to about 50° C. while the formation of the microporous membrane can be at temperatures ranging from about -10° C. to 50° C. Selection of appropriate operating parameters of temperature and solvent/co-solvent concentration can optimize the membrane at a given nominal pore size, flow rate, and polymer distribution.

45 citations

Patent
04 Jan 1990
TL;DR: In this paper, a thermal wave three-dimensional imaging and tomography apparatus and thermal wave detector therefor are provided, which includes a light source for generating a laser beam which is modulated and then focussed onto one side of a solid test material.
Abstract: A thermal wave three-dimensional imaging and tomography apparatus and a thermal wave detector therefor are provided. The apparatus includes a light source for generating a laser beam which is modulated and then focussed onto one side of a solid test material. A thin pyroelectric polymer electret (β-PVDF) film having an electroded upper surface and an electrodeless lower surface supports the other side of the test material on its electroded surface. A single thin metal elongate pin or an array of thin metal elongate pins are disposed beneath the electrodeless lower surface. The pin or pins generate(s) signals upon detection of thermal waves passing through the solid test material resulting from the laser excitation due to the photopyroelectric (P 2 E) effect. Since the pins are small, the signals generated by the pins represent local thermal wave progagation through the test material. The laser beam and the test material are moved relative to one another so that the laser beam scans substantially the entire one side of the test material. When using a single pin, the pin is moved with respect to the other side of the test material so that the pin scans the other side of the film to detect local thermal wave propagation through the test material during the entire scan of the laser beam on the test material. When using an array of pins, the array of pins remains stationary with respect to the other side of the material during the scan of the laser beam on the test material. The resulting signals generated by the pins during the laser beam scan are conveyed to a micro-computer via signal conditioning circuitry wherein a three-dimensional image of the test material subsurface structure is formed.

32 citations

Patent
21 Apr 1980
TL;DR: In this paper, a process for preparing polyvinylidene fluoride type (PVDF) films having highly stable piezoelectricity and pyroelectricity, by stretching PVDF films, while causing corona discharge, across the electric field formed by discharging, to effect thereby to polarization of film.
Abstract: A process for preparing polyvinylidene fluoride type (PVDF) films having highly stable piezoelectricity and pyroelectricity, by stretching PVDF films, while causing corona discharge, across the electric field formed by discharging, to effect thereby to polarization of film.

28 citations