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  • 1
    Digitale Medien
    Digitale Medien
    Zur Kriechstromfestigkeit (1970)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 1 (1970), S. 96-98 
    Details
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: Tracking ResistanceThe Standard methods for the determination of the Tracking resistance are discussed and from 36 different insulating-materials the “KB” value is measured, with electrode distances of 1, 2, 3 and 4 mm. From the results a change in the V.D.E. Standard 0110 definitions for the measurement of cleakage and air distances of electrical working materials is proposed: The “KA” value should be substituted by the “KB” value and the “KB” value should be specified for the 1 mm and 4 mm electrode distances.
    Notizen: Die genormten Methoden zur Bestimmung der Kriechstromfestigkeit werden diskutiert und an 36 verschiedenen Isolierstoffen die KB-Werte mit einem Elektrodenabstand von 1, 2, 3 und 4 mm gemessen. Aufgrund der Ergebnisse wird eine Änderung der VDE-Vorschrift 0110 “Bestimmungen für die Bemessung der Kriech und Luftstrecken elektrischer Betriebsmittel” vorgeschlagen: KA-Werte sollen durch KB-Werte ersetzt und die KB-Werte für 1 mm und 4 mm Elektrodenabstand angegeben werden.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mawe.19700010207
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  • 2
    Digitale Medien
    Digitale Medien
    Synthesis of poly(1.4.-benzamide) in solutions of randomly coiled polymers (1993)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 4 (1993), S. 385-392 
    Details
    ISSN: 1042-7147
    Schlagwort(e): Polycondensation ; Poly(1.4.-benzamide) ; Molecular composite ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: The polycondensation of p-aminobenzoic acid by the use of triphenylphospine and hexachloroethane is described. One way to obtain a mixed solution of rigid rod and flexible coil polymers is the polycondensation of the rigid chains in a solution of a flexible polymer matrix. Results on matrix polycondensation of poly(p-benzamide) in solutions of poly(methyl methacrylate), poly(methyl methacrylate-co-styrene), polystyrene and polyacrylonitrile are reported. It is shown that there exists an interrelation between the phase behavior of the mixed polymer solutions and the influence of the matrix polymer on the synthesis of poly(1.4.-benzamide). The ternary phase diagrams of the rigid rod/flexible coil polymer solutions were determined.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pat.1993.220040604
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  • 3
    Digitale Medien
    Digitale Medien
    Synthesis of aramides in solutions of poly(vinylpyrrolidone) (1993)
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 4 (1993), S. 496-501 
    Details
    ISSN: 1042-7147
    Schlagwort(e): Polycondensation ; Poly(1.4.benzamide) ; Molecular composite ; Phase diagram ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Results on polycondensation of poly(1.4 benzamide) (PBA) and 2.5.DCIPDAcoTPA in solutions of poly(vinylpyrrolidone) (PVP) will be presented. For polycondensation, the method of OGATA, using triphenylphosphine and hexachloroethane, and the low-temperature solution polycondensation of dicarboxylic acid dichlorides and diamines, were applied. It is shown that the molar mass of PBA depends strongly on the PVP:PBA ratio. To explain this dependence, one has to take into account the phase behavior of the ternary rigid rod polymer/flexible coil polymer/solvent system and the influence of the matrix polymer. An enhancement of the molar mass of the PBA produced can be observed when the PVP:PBA is high enough to prevent an association of the PBA, i.e. when one stays in the isotropic one-phase area of the phase diagram. Under these circumstances, it is possible to obtain one-phase systems in nonsolvents for the aramides.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/pat.1993.220040803
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  • 4
    Digitale Medien
    Digitale Medien
    Characteristic behavior of macro-, semimicro- and microelectrodes in voltammetric and chronoamperometric measurements (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 619-624 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Microelectrodes ; Chronoamperometry ; Resistive meolium ; Diffusion ; RAM electrode ; Graphite epoxy electrode ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The advantages of microelectrodes such as the improvement of signal-to-noise ratio, the ability to perform electrochemical measurements in high resistive solutions and small RC-time constants give the possibility of an extended use for voltammetric and chronoamperometric techniques in analytical chemistry. In this comparative study, the microelectrode properties of three selected electrodes were examined. The characterization of a RAM-microarray electrode, an epoxy-impregnated carbon electrode and a conventional glassy carbon macroelectrode was performed by cyclic voltammetry at different scan rates, by DP-voltammetric measurements using different concentrations of supporting electrolyte and by transient measurements. It could be shown, that in comparison to the microarray electrode and to the glassy carbon macroelectrode, respectively, the results obtained by using the epoxy-impregnated carbon electrode are caused by its semimicroelectrode character.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140090808
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  • 5
    Digitale Medien
    Digitale Medien
    Alternating current investigations at the mercury drop electrode on the adsorption potential of metal complexes (1996)
    Weinheim : Wiley-Blackwell
    Electroanalysis 8 (1996), S. 253-262 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Adsorption ; Alternating current measurements ; Adsorptive stripping voltammetry ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In adsorptive stripping voltammetry (AdSV) the analyte is accumulated on the electrode surface in the form of a metal complex and the determination step is carried out voltammetrically. Usually the technique is sensitive to the effects of other absorbable organic substances. Alternating-current (AC) investigations on the complexes of uranium, vanadium and antimony with chloranilic acid, uranium with cupferron and cobalt and nickel with dimethylglyoxime gave information about their adsorption behavior on the electrode surface. Furthermore the AC voltammetric behavior of the nonionic surfactant Triton X100 was shown. By knowing the adsorption potential and range of adsorption, predictions about the effects of organic adsorbates can be made. Importantly the optimal accumulation potential of the complex for its AdSV-determination may be obtained. With appropriate potential control the selective accumulation of the analyte complex can be achieved and so avoid the influence of these other adsorbates in favorable cases.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140080310
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  • 6
    Digitale Medien
    Digitale Medien
    AC-voltammetric determination of the total concentration of nonionic and anionic surfactants in aqueous systems (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 243-246 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Surfactants ; Tensammetry ; Adsorption ; Humic acid ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The tensammetric determination of the total concentration of mixtures of nonionic and anionic surfactants is desribed. By taking advantage of the different accumulation behavior of nonionic and anionic surfactants on the surface of the hanging mercury drop electrode (HMDE), it has been possible to determine the total concentration of nonionic surfactants without contribution from anionic surfactants. After subtraction of nonionic surfactant concentration from total, the concentration of anionic surfactants can be determined indirectly. Detection limits of 10 to 100 μg L-1 for single compounds and 100 μg L-1 for mixtures were calculated. Humic acids, relevant complexing reagents (like EDTA) and different cations do not interfere in the determination when they are present in typical concentrations found in surface waters. The method has been applied to several mixtures of surfactants. The possibility of solid-phase-extraction (SPE) for sample pretreatment has been investigated.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140090311
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  • 7
    Digitale Medien
    Digitale Medien
    Functionality type analysis of carboxy-terminated oligostyrenes by gradient high performance liquid chromatography (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 3365-3376 
    Details
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Carboxy-terminated oligostyrenes, prepared by radical polymerization using a dicarboxy-functional initiator, can efficiently be separated by gradient high performance liquid chromatography (HPLC). On a normal phase chromatographic system, comprising a silica gel stationary phase and a tetrahydrofuran-hexane eluent, elution occurs in the order of increasing polarity of the oligomers and separation into non-, mono-, and dicarboxy oligomer fractions is obtained. The chemical structure of the different functionality fractions is determined by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS). The results indicate that further functionality fractions in addition to the carboxy oligomers are formed, due to contamination of the initiator or side reactions during the polymerization process.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/macp.1997.021981103
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  • 8
    Digitale Medien
    Digitale Medien
    Application of adsorptive stripping voltammetry to trace measurements of molybdenum in plant materials (1993)
    Weinheim : Wiley-Blackwell
    Electroanalysis 5 (1993), S. 623-625 
    Details
    ISSN: 1040-0397
    Schlagwort(e): Molybdenum ; Plant materials ; Adsorptive stripping voltammetry ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A procedure is presented for quantifying molybdenum in dry ashed plant samples. The determination is made by adsorptive stripping voltammetry in the differential pulse mode (DPAdSV). It is based on the adsorptive accumulation of the Mo(VI)-chloranilic acid complex on the surface of a hanging mercury drop, followed by the reduction of the adsorbed complex. Optimal conditions are stirred acidified supporting electrolyte solution (of pH 2-3), containing 10-3 mol/L chloranilic acid and an accumulation potential of -0.20 V (vs. Ag/AgCl, 3 mol/L KCl). The height of the cathodic stripping peak around -0.60 V depends linearly on the molybdenum concentration and accumulation time (over the ranges 0-12 ng/ml and 0-300 seconds, respectively). For an accumulation period of 5 minutes, the detection limit is 0.02 ng/ml. Possible interferences by other trace metals are investigated. The proposed procedure has been applied to the determination of molybdenum traces in a variety of plants with good accuracy and precision. The results are in good agreement with those obtained by atomic absorption spectrometry.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/elan.1140050717
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