The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform
Johnathan A Hiltz - One of the best experts on this subject based on the ideXlab platform.
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characterization of fluoroelastomers by various analytical techniques including pyrolysis gas chromatography mass spectrometry
Journal of Analytical and Applied Pyrolysis, 2014Co-Authors: Johnathan A HiltzAbstract:Abstract Fluorocarbon elastomers are specified for a number of applications where excellent high temperature and chemical resistance is required. To ensure that a fluoroelastomer with the required properties for a particular application is used, characterization techniques that allow the positive identification of the elastomer are required. In this paper the characterization of four fluoroelastomer formulations – a Vinylidene fluoride/hexafluoropropene (VDF/HFP) dipolymer, a Vinylidene fluoride/hexafluoropropene/tetrafluoroethylene terpolymer, and two Vinylidene fluoride/perfluoro(methyl vinyl ether)/tetrafluoroethylene (VDF/PMVE/TFE) tetrarpolymers – is described. The characterization techniques included pyrolysis gas chromatography/mass spectrometry (py-GC/MS), Fourier transform infrared (FT-IR) spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Py-GC/MS was the only characterization technique that could identify the four formulations unambiguously. The positive identification was based on differences in the pyrolytic degradation products of the flouroelastomer formulations.
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Characterization of fluoroelastomers by various analytical techniques including pyrolysis gas chromatography/mass spectrometry☆
Journal of Analytical and Applied Pyrolysis, 2014Co-Authors: Johnathan A HiltzAbstract:Abstract Fluorocarbon elastomers are specified for a number of applications where excellent high temperature and chemical resistance is required. To ensure that a fluoroelastomer with the required properties for a particular application is used, characterization techniques that allow the positive identification of the elastomer are required. In this paper the characterization of four fluoroelastomer formulations – a Vinylidene fluoride/hexafluoropropene (VDF/HFP) dipolymer, a Vinylidene fluoride/hexafluoropropene/tetrafluoroethylene terpolymer, and two Vinylidene fluoride/perfluoro(methyl vinyl ether)/tetrafluoroethylene (VDF/PMVE/TFE) tetrarpolymers – is described. The characterization techniques included pyrolysis gas chromatography/mass spectrometry (py-GC/MS), Fourier transform infrared (FT-IR) spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Py-GC/MS was the only characterization technique that could identify the four formulations unambiguously. The positive identification was based on differences in the pyrolytic degradation products of the flouroelastomer formulations.
R. Chûjô - One of the best experts on this subject based on the ideXlab platform.
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A MOLECULAR MECHANICS STUDY OF PIEZOELECTRIC ACTIVITY OF Vinylidene CYANIDE COPOLYMERS
Computer Aided Innovation of New Materials II, 1993Co-Authors: Minoru Sakurai, Y. Ohta, Yoshio Inoue, R. ChûjôAbstract:The MM2 calculation is applied in order to study the chain flexibility of Vinylidene cyanide copolymers having high piezoelectric activity: poly(Vinylidene cyanide- co -vinyl acetate) and poly(Vinylidene cyanide- co -methyl methacrylate). The main chain of the former copolymer is shown to be more flexible than that of the latter, suggesting that the piezoelectric activity of Vinylidene cyanide copolymers depends on chain mobility.
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An important factor generating piezoelectric activity of Vinylidene cyanide copolymers
Polymer communications, 1991Co-Authors: Minoru Sakurai, Y. Ohta, Yoshio Inoue, R. ChûjôAbstract:Potential energy maps are obtained as a function of backbone rotational angles for two types of Vinylidene cyanide copolymers showing different piezoelectricity:poly(Vinylidene cyanide-co-vinyl acetate) and poly(Vinylidene cyanide-co-methyl methacrylate). The rotational barrier height and the location of energy minima are compared for the two types of copolymer. It is suggested that the piezoelectricity of these copolymers depends on chain mobility
Henry F. Schaefer - One of the best experts on this subject based on the ideXlab platform.
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isomerization reactions on the lowest potential energy hypersurface of triplet Vinylidene and triplet acetylene
Journal of Chemical Physics, 1993Co-Authors: George Vacek, Russell J Thomas, Bradley J Deleeuw, Yukio Yamaguchi, Henry F. SchaeferAbstract:Triplet Vinylidene, first predicted to have a sizeable barrier to unimolecular rearrangement in 1978 by theory, has now been observed under three different sets of experimental conditions. In order to quantitatively characterize the potential energy hypersurface of triplet Vinylidene and triplet acetylene, high‐level ab initio quantum mechanical methods have been employed. Basis sets as large as triple zeta plus two sets of polarization functions augmented with higher angular momentum functions [TZ(2df,2pd)] have been utilized in conjunction with correlated methods as sophisticated as the coupled cluster approach including all single, double, and perturbative triple excitations [CCSD(T)]. Of particular interest are predictions of the zero‐point vibrational energy corrected barriers for rearrangement of a 3B2 Vinylidene to b 3Bu trans‐bent acetylene and of cis‐bent a 3B2 acetylene to trans‐bent b 3Bu acetylene. At the highest level of theory used here, TZ(2df,2pd) CCSD(T), these are predicted to be 47....
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Vinylidene: The final chapter
Journal of the American Chemical Society, 1990Co-Authors: Mary M. Gallo, Tracy P. Hamilton, Henry F. SchaeferAbstract:Ab initio molecular electronic structure theory is used to study the electronic ground state Vinylidene-acetylene isomerization. Vinylidene, acetylene, and the transition state connecting them are located at various levels of theory, including correlated levels, and with large basis sets. The highest level and basis set with which geometry optimizations are performed is the CCSD level with the TZ+2P basis set. These structures are characterized by harmonic vibrational analyses as minima or transition states. Single-point energies also are computed at higher levels of theory, the highest being CCSD/QZ+3P, for all three structures. The effects of carbon atom f functions and hydrogen atom d functions are also explicitly considered. A classical barrier to isomerization from Vinylidene to acetylene of {approximately}3 kcal/mol is found. The {Delta}E for isomerization is predicted to be {approximately}43 kcal/mol.
Bruno Ameduri - One of the best experts on this subject based on the ideXlab platform.
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Combination of Cationic and Radical RAFT Polymerizations: A Versatile Route to Well-Defined Poly(ethyl vinyl ether)-blockpoly(Vinylidene fluoride) Block Copolymers
ACS Macro Letters, 2017Co-Authors: Marc Guerre, Mona Semsarilar, Mineto Uchiyama, Enrique Folgado, Kotaro Satoh, Masami Kamigaito, Bruno Ameduri, Vincent LadmiralAbstract:Poly(Vinylidene fluoride)-containing block copolymers are difficult to prepare and still very rare in spite of their potential use in high added value applications. This communication describes in detail the synthesis of unprecedented poly(ethyl vinyl ether)-block-poly(Vinylidene fluoride) (PEVE-b-PVDF) block copolymers (BCP) via the sequential combination of cationic RAFT polymerization of vinyl ethers and radical RAFT polymerization of Vinylidene fluoride (VDF). Dithiocarbamate chain transfer agents were found to efficiently control the radical RAFT polymerization of VDF and to be suitable for the preparation of PEVE-b-PVDF BCP. These new block copolymers composed of incompatible polymer segments may find applications owing to their phase segregation and self-assembly behavior.
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DIELECTRIC PROPERTIES OF BLOCK COPOLYMERS BASED ON Vinylidene FLUORIDE AND CYANO COMONOMERS
Journal of Non-Crystalline Solids, 2010Co-Authors: Ahmed Meskini, Mustapha Raihane, Isabelle Stevenson, Gisèle Boiteux, Gérard Seytre, Bruno AmeduriAbstract:The synthesis of poly(Vinylidene fluoride)-b-poly(AN, MAN, VCN) (PVDF-b-MCN) block copolymers, using the iodine transfer polymerization (ITP) of Vinylidene cyanide, acrylonitrile and méthacrylonitrile, in the presence of PVDF-I, are presented. In a first step, the ITP of Vinylidene fluoride in the presence of C6F13I as the chain transfer agents leads to two different isomeric oligomers (PVDF-I), bearing either -CH2I or –CF2I end-groups. The ITP of cyanide monomers (MCN) using those latter fluorinated oligomers as macromolecular chain transfer agents, were achieved as shown in scheme below. The characterization of sampled aliquots by 19F and 1H NMR spectroscopy could monitor the average degree of polymerization in number versus cyanide monomers conversions. ITP of cyanide monomers. These block copolymers were characterized by 19F and 1H NMR and by SEC chromatography. Their thermal properties were also studied by differential scanning calorimetry (DSC), respectively.
Gerhard Rittmayer - One of the best experts on this subject based on the ideXlab platform.
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Vinylidene fluoride polymers and Vinylidene fluoride trifluoroethylene copolymers
1990Co-Authors: Johann Kammermaier, Gerhard RittmayerAbstract:Coatings comprising Vinylidene fluoride polymers or Vinylidene fluoride-trifluoroethylene copolymers can be produced in a thickness of mol/cm is subjected to low-pressure plasma polymerisation excited by microwaves, and the polymer or copolymer is deposited on a substrate at an electrical field strength of < 850 V/cm.
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method of preparing layers of Vinylidene fluoride polymers and Vinylidene fluoride trifluoroethylene copolymers on a substrate
1990Co-Authors: Johann Kammermaier, Gerhard RittmayerAbstract:Layers consisting of Vinylidene fluoride polymers or Vinylidene fluoride/trifluoroethylene copolymers can be prepared with a thickness of <10 μm, whereby the dielectric constant or the ferroelectric properties simultaneously correspond to those of known materials. Vinylidene fluoride or a mixture of Vinylidene fluoride and trifluoroethylene in a concentration of ≦5×10-9 mol/cm3 is subjected to a low pressure plasma polymerization which is excited by microwaves, and the polymer or copolymer is deposited onto a substrate at an electric field strength of <850 V/cm.