Abstract: A flexible security document is provided which contains an authentication device including: a) source of electrical potential (5), the source including a piezoelectric polymeric material including at least one terpolymer of vinylidene fluoride (VDF), trifluoroethylene (TrFE) and a halogenated ethylene based monomer containing at least one non-fluorine halogen atom, the source of electrical potential being activated by mechanical deformation; b) reporter element (3) including a material capable of switching electrically between a first state and a second state, the difference between the first state and the second state being able to be perceived by an unaided human; and c) conducting elements (8) electrically connecting the source of electrical potential and the reporter element to produce an electric circuit.

Abstract: A process for manufacturing terpolymers by polymerization of VDF (vinylidene difluoride), TrFE (trifluoroethylene), and CFE (1-chloro-1-fluoroethylene) or CTFE (chlorotrifluoroethylene) monomers in the presence of a radical polymerization initiator, characterized in that: i) an initial mixture of VDF and of TrFE, free of CFE and of CTFE, is fed into an autoclave, ii) the initiator mixed with water is injected into the autoclave so as to achieve, inside the autoclave, a pressure at least equal to 80 bar, in order to form a suspension of VDF and TrFE monomers in water, iii) a secondary mixture constituted of VDF, TrFE and CFE or CTFE is injected into the autoclave, then iv) as soon as the polymerization reaction starts, said secondary mixture is reinjected continuously into the reactor, so as to maintain therein a constant pressure of at least 80 bar.

Abstract: A process for manufacturing terpolymers by polymerization of VDF (vinylidene difluoride), TrFE (trifluoroethylene), and CFE (1-chloro-1-fluoroethylene) or CTFE (chlorotrifluoroethylene) monomers in the presence of a radical polymerization initiator, characterized in that: i) an initial mixture of VDF and of TrFE, free of CFE and of CTFE, is fed into an autoclave, ii) the initiator mixed with water is injected into the autoclave so as to achieve, inside the autoclave, a pressure at least equal to 80 bar, in order to form a suspension of VDF and TrFE monomers in water, iii) a secondary mixture constituted of VDF, TrFE and CFE or CTFE is injected into the autoclave, then iv) as soon as the polymerization reaction starts, said secondary mixture is reinjected continuously into the reactor, so as to maintain therein a constant pressure of at least 80 bar.

Abstract: A process for manufacturing terpolymers by polymerization of VDF (vinylidene difluoride), TrFE (trifluoroethylene), and CFE (1-chloro-1-fluoroethylene) or CTFE (chlorotrifluoroethylene) monomers in the presence of a radical polymerization initiator, characterized in that: i) an initial mixture of VDF and of TrFE, free of CFE and of CTFE, is fed into an autoclave, ii) the initiator mixed with water is injected into the autoclave so as to achieve, inside the autoclave, a pressure at least equal to 80 bar, in order to form a suspension of VDF and TrFE monomers in water, iii) a secondary mixture constituted of VDF, TrFE and CFE or CTFE is injected into the autoclave, then iv) as soon as the polymerization reaction starts, said secondary mixture is reinjected continuously into the reactor, so as to maintain therein a constant pressure of at least 80 bar.

Abstract: A process for manufacturing terpolymers by polymerization of VDF (vinylidene difluoride), TrFE (trifluoroethylene), and CFE (1-chloro-1-fluoroethylene) or CTFE (chlorotrifluoroethylene) monomers in the presence of a radical polymerization initiator, characterized in that: i) an initial mixture of VDF and of TrFE, free of CFE and of CTFE, is fed into an autoclave, ii) the initiator mixed with water is injected into the autoclave so as to achieve, inside the autoclave, a pressure at least equal to 80 bar, in order to form a suspension of VDF and TrFE monomers in water, iii) a secondary mixture constituted of VDF, TrFE and CFE or CTFE is injected into the autoclave, then iv) as soon as the polymerization reaction starts, said secondary mixture is reinjected continuously into the reactor, so as to maintain therein a constant pressure of at least 80 bar.

Abstract: A method of manufacturing, by suspension polymerization, dielectric copolymers, including injecting an initial mixture of constituent monomers into an autoclave at constant temperature and pressure, wherein the mixture of constituent monomers including vinylidene difluoride (VDF), trifluoroethylene (TrFE), and a monomer 2 to 10 times more reactive than VDF and TrFE; and continuously reinjecting at constant pressure, as soon as the reaction is initiated and throughout the duration of polymerization, a second mixture of the constituent monomers, wherein the molar composition of the initial mixture and the second mixture are determined by calculation, in a manner known of itself, taking into account the desired molar composition of the copolymer and the higher reactivity of the third monomer.

Abstract: A flexible security document is provided which contains an authentication device including: a) source of electrical potential (5), the source including a piezoelectric polymeric material including at least one terpolymer of vinylidene fluoride (VDF), trifluoroethylene (TrFE) and a halogenated ethylene based monomer containing at least one non-fluorine halogen atom, the source of electrical potential being activated by mechanical deformation; b) reporter element (3) including a material capable of switching electrically between a first state and a second state, the difference between the first state and the second state being able to be perceived by an unaided human; and c) conducting elements (8) electrically connecting the source of electrical potential and the reporter element to produce an electric circuit.

Abstract: A method of manufacturing, by suspension polymerization, dielectric copolymers, including injecting an initial mixture of constituent monomers into an autoclave at constant temperature and pressure, wherein the mixture of constituent monomers including vinylidene difluoride (VDF), trifluoroethylene (TrFE), and a monomer 2 to 10 times more reactive than VDF and TrFE; and continuously reinjecting at constant pressure, as soon as the reaction is initiated and throughout the duration of polymerization, a second mixture of the constituent monomers, wherein the molar composition of the initial mixture and the second mixture are determined by calculation, in a manner known of itself, taking into account the desired molar composition of the copolymer and the higher reactivity of the third monomer.

Abstract: Process for polarizing at least a part of a ferroelectric material in a cylindrical shape having a longitudinal axis, and having an internal conductor inside the cylinder disposed along the longitudinal axis. At least part of said cylinder is placed in a conductive liquid with the cylinder being free from any stresses other than pressure exerted by the conductive liquid. A low frequency AC voltage is then applied between an electrode in contact with the conductive liquid and the internal conductor, and the amplitude of the voltage is increased progressively up to a value such that an electrical field is created having an amplitude greater than a coercive field of polarization Ec of the ferroelectric material.

Abstract: Process for polarizing at least a part of a ferroelectric material in a cylindrical shape having a longitudinal axis, and having an internal conductor inside the cylinder disposed along the longitudinal axis. At least part of said cylinder is placed in a conductive liquid with the cylinder being free from any stresses other than pressure exerted by the conductive liquid. A low frequency AC voltage is then applied between an electrode in contact with the conductive liquid and the internal conductor, and the amplitude of the voltage is increased progressively up to a value such that an electrical field is created having an amplitude greater than a coercive field of polarization Ec of the ferroelectric material.

Abstract: A method of polarizing selected areas of a foil of ferroelectric material, wherein electrodes are deposited in such a way on the opposite surfaces of the foil that the zone to be polarized extends between these two electrodes. The zone to be polarized is compressed and a variable voltage is applied across the electrodes. Each electrode is connected to an insulating support whose surface exceeds that of the zone to be polarized on the foil of ferroelectric material. Besides the electrode, the insulating support has a layer of dielectric material whose external surface is level with the external surface of the electrode.

Abstract: An electrical procedure depolarizes completely or partially a ferroelectric material which had been polarized before in at least one of its regions. A low-frequency alternating electric field is applied to the material whose amplitude exceeds the coercive field E.sub.c and is then decreased step by step. In a preferred embodiment the selected maximum value is 1.3 times that of the coercive field E.sub.c. It is also possible to depolarize the material selectively so that there are polarized zones remaining. The procedure may be applied to produce materials for piezoelectric or pyroelectric transducers as well as to obtain materials with improved dielectric strength.

Abstract: Means for polarizing ferroelectric materials up to a predetermined polarization level include the application of an electric field E to these materials. According to this method the ferroelectric material is subjected to an alternating electric field E, the frequency of which ranges from about 0.001 to 1 Hz, and which is made to increase gradually and in a cyclic way between 0.+-.E.sub.N, E.sub.N being slightly in excess of the coercive force E.sub.C of said material. Simultaneously, the intensity i of the current traversing the material (2) is measured as a function of the applied field (E) using a unit of visualization, until a stable curve i=f(E) is attained. The invention is particularly suitable for obtaining a stable polarization of ferroelectric polymers, copolymers, crystals, and polycrystals, with the objective of using the piezoelectric and/or pyroelectric properties of these materials.

Abstract: Method and means for polarizing ferroelectric materials up to a predetermined polarization level include the application of an electric field E to these materials. According to this method the ferroelectric material is subjected to an alternating electric field E, the frequency of which ranges from about 0.001 to 1 Hz, and which is made to increase gradually and in a cyclic way between 0.+-.E.sub.N, E.sub.N being slightly in excess of the coercive force E.sub.C of said material. Simultaneously, the intensity i of the current traversing the material (2) is measured as a function of the applied field (E) using a unit of visualization, until a stable curve i=f(E) is attained. The invention is particularly suitable for obtaining a stable polarization of ferroelectric polymers, copolymers, crystals, and polycrystals, with the objective of using the piezoelectric and/or pyroelectric properties of these materials.