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  • 1
    Publication Date: 1978-06-01
    Print ISSN: 0372-820X
    Electronic ISSN: 1435-1536
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 2
    Publication Date: 1984-01-01
    Print ISSN: 0360-3199
    Electronic ISSN: 1879-3487
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Elsevier
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  • 3
    Publication Date: 1982-01-01
    Print ISSN: 0021-9797
    Electronic ISSN: 1095-7103
    Topics: Chemistry and Pharmacology , Physics
    Published by Elsevier
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 256 (1978), S. 544-551 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Zusammenfassung Die eislösenden Eigenschaften einer Serie von Polydimethylsiloxanen-Polycarbonaten Block-Copolymer Filmen wurde studiert. Die Abhäsion ist nicht nur eine Funktion der hydrophobischen Eigenschaften der Filme sondern ist auch abhängig von dem Polysiloxan-Anteil, ihrer Block-Länge und Glas-Temperatur, das heißt sie hängt auch von den rheologischen Eigenschaften der Filme relativ zum Eise ab. Zugabe von etwas Silicon-Öl zu den Filmen verbessert nur die Abbäsion der optimalen Block-Copolymeren, die einen günstigen Polydimethylsiloxane-Gehalt haben. Das Öl wirkt als „Plasticizer” und Schmiermittel. Messungen der Infrarot-Reflektionen zeigen, daß das Polydimethylsiloxan hauptsächlich in der Polymer/Luft-Grenzfläche liegt und im besonderen, daß die Methyl-Gruppen zuoberst liegen.
    Notes: Summary The ice releasing characteristics of a series of polydimethylsiloxane-polycarbonate block-copolymers films have been investigated. The abhesion is not only a function of the hydrophobic nature of the surface of the films but is also dpendent of the polysiloxane content, its block chain length and the glass temperature of the polymer, i. e. it is dependent on the rheological properties of the films telative to ice. Addition of some silicone oil to the films only improves the abhesion of the optimum block-copolymers which have a suitable polydimethylsiloxane composition. The oil acts as plasticizer and lubricant. Attenuated infrared reflectance measurements show that the polydimethylsiloxane blocks lie preferentially in the polymer/air interface, i. e. the methyl groups are located uppermost.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 1493-1522 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidative degradation of isotactic polypropylene films coated on well-defined Cu(Cu2O), CuO0.67, and CuO films in a temperature range of 90-120°C in a quartz-spoon-gauge-reaction vessel was studied. This catalytic reaction has been compared with the oxidation of polypropylene without copper or oxide films. The reaction vessel contained, if needed, P2O5 and/or KOH as “getters” for H2O and CO2, these substances could be menitored continuously. Cu(Cu2O) films were transformed during oxidation of the polymer to yellow CuO0.67 below 100°C and above this temperature to black CuO in the presence of H2O and CO2, whereas in the absence of these compounds CuO was formed below 100°C and CuO0.67 at 120°C. Characteristic autoxidation curves obtained in the absence of H2O and CO2 showed induction periods that were shorter for copper oxide-polymer interfaces than for glass-polymer interfaces (i.e., for uncatalyzed oxidation). Abnormalities were observed for Cu(Cu2O)-polymer interfaces because of further oxidation of Cu during the reaction. The rates of oxygen consumption were faster for CuO0.67-polymer and CuO-polymer than for the uncatalyzed reaction; the catalytic action of CuO0.67 was somewhat larger than that of CuO. The important observation was made that the mechanism of oxidation is not the same in the absence and presence of reaction products; that is, H2O and CO2. This was confirmed by ion beam scattering experiments, which also revealed that an oxidation-reduction process takes place at Cu and their oxide interfaces. A mechanism for the catalytic oxidation process, based on the ease by which copper ions are released from the metal oxides at the interface, was formulated. These ions diffuse subsequently as actions of carboxylate anions into the bulk of the polymer. Arrhenius equations of oxygen consumption are given for all cases; the energy of activation calculated for the initiation of the uncatalyzed oxidation agrees with its literature value. The energy of activation for the initiation of the catalyzed reaction was a few kilocalories lower than that for the uncatalyzed reaction. Catalytic action is mainly operative for the initiation reaction at the interface and for the decomposition of hydroperoxides by copper ions. Preventing the delivery of copper ions to the polymer would be the most efficient way of inhibiting the catalysis.
    Additional Material: 29 Ill.
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  • 6
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: IR specular reflectance spectra with respect to hydrogen peroxide formation during uncatalyzed and Cu (oxide)-catalyzed oxidation of isotactic Polypropylene films have been measured as function of time and temperature (90-130°C). Energies of activation for the various cases have been obtained. The originally proposed kinetic scheme based on oxygen-absorption measurements has been modified in order to accommodate the spectroscopical results. The amount of ROOH groups present at any time on the polymer is very small, indicating relatively slow rates of ROOH formation and fast rates of their decomposition. The kinetic scheme fits well the experimental data. However, the reasons for the variations of the relevant energies of activation obtained for the catalyzed oxidation in absence and presence of the main volatile reaction products, H2O and CO2, are not yet understood, i.e., the mechanism needs further investigations.
    Additional Material: 9 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 17 (1979), S. 2031-2038 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nylon 66 films with varying spherulite size but almost constant percentages of crystallinity were prepared (melt method). These films were degraded by NO2 over a range of temperatures from 35 to 65°C. Random chain scission took place except in the initial stages at low temperatures at which some crosslinking occurred. Observation of the films with the extent of degradation under polarized light revealed that dark bands developed around and also inside spherulite boundaries that became wider with the extent of degradation. This indicates that amorphous material is formed during random chain scission; the spherulites remained practically intact, however. The experimental chain scission rate constants did not change essentially with spherulite diameter until small diameters were reached, at which time the rate constants increased noticeably. Degradation can be accounted for by chain scission in amorphous and interfacial regions; in the latter the rate constants increased with this area and in addition main chain links were weaker in fold regions, due to strain energy, than normal ones in amorphous regions. The energy of activation for chain scission was compatible with a predominantly diffusion-controlled process.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 2963-2972 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Instruments have been developed for the testing of stiffness of polymers in various gaseous environmental “atmospheres” over a large range of temperatures. They are based on the cantilever principle, where a small strip of a specimen is deflected statically or periodically. Changes in stiffness are measured as function of the bending force or power input, respectively. The dynamic instrument responds very sensitively to the onset of cracking in specimens due to ozone exposure. The static instrument is well suited for measuring the onset of rapidly increasing stiffness as temperatures are lowered.
    Additional Material: 10 Ill.
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  • 9
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der thermische Abbau von Polytetrafluoräthylen wurde in einem geschlossenen System im Temperaturbereich von 480 bis 580°C studiert. Der Beginn der Gasentwicklung folgt einem Gesetz erster Ordnung. Wenn die Dimerisation des Monomeren zu Octafluorbutan berücksichtigt wird, dann können die Geschwindigkeitskonstanten durch die Beziehung k = 6,3·1019 e-78000/RT min-1 ausgedrückt werden.
    Notes: The thermal degradation of polytetrafluoroethylene has been studied in a closed reaction system over a temperature range from 480 to 580°C. The initial stages of gas formation follow a first order law. If the dimerization of monomer to octafluorocyclbutane is taken into account, the rate constants for polymer degradation can be represented by k = 6.3·1019 e-78,000/RT min-1.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 19 (1981), S. 1131-1139 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An apparatus for determination of regression (weight-loss) rates before, at, and after ignition as a function of oxidant gas flow rates has been constructed and successfully operated with poly(methyl methacrylate). In addition, flame temperatures, gas evolution kinetics and composition can be ascertained. The apparatus allows a proper evaluation of diffusion processes and chemically controlled processes. The regression rate for PMMA is directly proportional to the air flow rate. At low air flow rates the process is diffusion controlled and the energy of activation is identical with the heat of vaporization of the monomer. There is a liquid monomer layer and on top of it a stagnant vapor layer having the equilibrium vapor pressure of the monomer. At higher flow rates the energy of activation increases steeply. The layers become thin and defective and eventually thermal depolymerization becomes rate determining. This depolymerization has an energy of activation between 30 to 40 kcal mol-1. Experiments have also been carried out in closed quartz tubes. Explosion limits, ignition lags and energies of activation have been determined. The latter were evaluated by the method of Semenoff.
    Additional Material: 8 Ill.
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