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  • 1
    Series available for loan
    Series available for loan
    Hanover, NH : Corps of Engineers, U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-317
    In: Research report
    Description / Table of Contents: Experiments by Smith-Johannsen on the adhesion of ice frozen from a number of 1 x 10^-3 ? electrolyte solutions to a wax-treated aluminum surface at -10°C are discussed. It is concluded that the adhesive strength measured by the force per square centimeter needed to shear the ice off the substrate surface is mainly due to a liquid interfacial solution layer between the ice and the substrate surface. The thickness of such a layer is largely determined by the same considerations as the thickness of grain boundary layers in ice obtained from dilute electrolyte solutions.
    Type of Medium: Series available for loan
    Pages: ii, 9 S. : graph. Darst.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 317
    Branch Library: AWI Library
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  • 2
    Series available for loan
    Series available for loan
    Hanover, NH : U.S. Army Cold Regions Research and Engineering Laboratory
    Associated volumes
    Call number: ZSP-202-321
    In: Research report
    Description / Table of Contents: CONTENTS: Introduction. - Tensile strength apparatus. - Synthesis of linear polyurethane. - Tensile strength of polyurethane films. - Preparation of films and technique of measuring tensile strength. - Results. - Effect of N02 on polyurethane films. - Stiffness testers. - Static apparatus. - Experimental results. - Dynamic "stiffness" tester. - Summary. - Conclusion. - Literature cited. - Abstract.
    Description / Table of Contents: A tensile strength, a static and a dynamic stiffness tester have been constructed for measuring appropriate mechanical properties of polymers as a function of temperature, environmental conditions (i.e. air plus NO2, O3, etc. or of the pollutants alone), exposure time and pollutant concentration. The apparatus were found to perform satisfactorily. The dynamic stiffness tester is particularly sensitive to the onset of cracking in polymeric materials due to ozone. The tensile strength of linear polyurethane was affected appreciably by NO2 alone and also by NO2 in presence of air. Chain scission cross-linking, evolution of CO2 and other small molecular weight compounds, and formation of nitro and nitroso groups along the polymer backbone are reactions underlying the observed changes in mechanical properties of the polymer. The static "stiffness" tester allows one to measure "stiffness" (Young's modulus) of polymers (especially elastomers) as a function of the above-mentioned parameters. A preliminary selection of polymeric skirting materials for SEV's can be made on the basis of results obtained as functions of temperature. Two industrial samples appeared to be suitable for this purpose on the basis of results obtained. "Stiffness" of these samples started to increase rapidly only at -40°C and -30°C whereas others became brittle at higher temperatures. The dynamic stiffness tester was tested with a natural rubber compound because of its susceptibility to ozone. Onset of cracking was accurately and clearly indicated by this instrument. An EPM compound proved quite resistant to ozone over prolonged periods of time. Time did not allow tests to be comipleted on all the compounds supplied by industry.
    Type of Medium: Series available for loan
    Pages: iv, 26 S. : Ill., graph. Darst.
    Series Statement: Research report / Cold Regions Research and Engineering Laboratory, CRREL, US Army Material Command 321
    Branch Library: AWI Library
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  • 3
    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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  • 4
    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
    Type of Medium: Electronic Resource
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  • 5
    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
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 253 (1975), S. 182-182 
    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
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 202 (1965), S. 1-10 
    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 Der Photoabbau von Polymethylmethacrylat-Lösungen in 2-Chloräthanol wurde in Abhängigkeit von der Bestrahlungszeit, Konzentration des Polymeren, Temperatur und Lichtintensität untersucht. Die Reaktion für Initiierung des statistischen Kettenbruchs hängt von der Konzentration des Polymeren ab. Mit steigender Temperatur (54–159
    Notes: Summary The photodegradation of polymethylmethacrylate solutions in 2-chloroethanol has been investigated as a function of irradiation time, polymer concentration, temperature and light intensity. The random chain scission initiation reaction is dependent on polymer concentration. At elevated temperatures (54
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 232 (1969), S. 758-763 
    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 Das Sorbieren von Wasser an Polyacrylonitril, Polymethylmethacrylat, ataktisches und isotaktisches Polystyrol wurde in einem Temperaturgebiet von negativen bis zu positiven Werten (in der Nähe von 0 °C) gemessen. Für Polyvinylpyrrolidon wurde es nur bei drei Temperaturen gemessen (−2, +7, +10 °C). Isosterische Wärmen und Entropien wurden als Funktion der Flächenbedeckung ausgewertet. Für Polyacrylonitril und Polymethylmethacrylat wurde gezeigt, daß das absorbierte Wasser für Bedeckungen kleiner als eine monomolekulare Schicht schwächer gebunden ist als Wasser zu kondensiertem Wasser; die Ordnung ist auch kleiner als im kondensierten Wasser. Die Konstanten der BET-Gleichung sind im Einklang mit den Schlüssen, die von den isosterischen Wärmen und von den Adsorptions-Entropien gezogen werden können. Ataktisches und isotaktisches Polystyrol absorbieren kein Wasser unter einem relativen Druck von 0.85 und nur sehr wenig bei höheren Drucken. PVP ist ein besonderer Fall, da es wasserlöslich ist. Die Isothermen sind von der Temperatur unabhängig. Sie sind der „Isothermen“ ähnlich, die in einer früheren Arbeit für „gebundenes“ Wasser beim Gefrieren von PVP-Lösungen gefunden wurde. Der Schluß kann gezogen werden, daß Wasser, das absorbiert oder von PVP gebunden ist, eine Struktur ähnlich dem Eis aufweist.
    Notes: Summary Sorption of water has been measured for polyacrylonitrile, polymethylmethacrylate, and atactic and isotactic polystyrene over a range of temperatures from negative to positive degrees centigrade and for polyvinylpyrrolidone at −2 °C, +7 °C and +10 °C. The isosteric heats and differential molar entropies as function of coverage show in the cases of polyacrylonitrile and polymethylmethacrylate that water below monolayer coverage is less strongly bound and of less order then condensed water. At about one monolayer coverage, the sorption goes over to condensation of water. Parameters derived from the BET equation are in agreement with the conclusions derived from isosteric heats and entropies of adsorption. Atactic and isotactic polystyrene do not sorb water at all up to a relative pressure of 0.85 but adsorb some water at higher relative pressures. Polyvinylpyrrolidone is a special case, as it is water soluble. The sorption isotherms have a zero temperature coefficient. They are similar to the “isotherm” previously obtained for “bound” water in freezing PVP solutions. The conclusion is reached that water sorbed on or “bound” to PVP has an ice-like structure.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 253 (1975), S. 340-340 
    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
    Type of Medium: Electronic Resource
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  • 10
    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: Die Geschwindigkeitskonstanten des thermischen Abbaus von Polymethylmethacrylatfraktionen wurden in einem weiten Temperaturbereich gemessen und die ARRHENIUS-Gleichungen abgeleitet. Es existieren zwei Abbaureaktionen Für dieses Polymere: eine „schnelle“ Reaktion, die vom Kettenende her beginnt und Molekülen mit Doppelbindung am Kettenende zuzuschreiben ist, ferner eine „langsame“ Reaktion, die statistisch beginnt. Die Aktivierungsenergie der schnellen Reaktion ist wesentlich niedriger als die der langsamen Reaktion. Beide zeigen zwei Stufen der Aktivierungsenergie, fortschreitend von langen zu kurzen Ketten. Diese Aktivierungsenergien steigen mit abnehmender KettenIänge an, wie es theoretisch zu erwarten ist. Während die Energiedifferenzen Für die schnelle Reaktion mit einem Mechanismus „Start am Kettenende - Abbaureaktion - Abbruch nach der 2. Reaktionsordnung“ in Übereinstimmung stehen, wird ein vernünftiger Wert für die Gesamtenergie bei der langsamen Reaktion nur mit einem Abbruchsprozeß nach der 1. Reaktionsordnung erhalten. Solch eine Reaktion ist nicht unwahrscheinlich, da der Polymerfilm in diesem Abbaustadium merkliche Mengen an Monomerem enthält. Die Aktivierungsenergien der langsamen Reaktion wachsen mit dem Prozentsatz der Umsetzung, solange noch einige Kettenenden mit Doppelbindung im System enthalten sind. Es muß gefolgert werden, daß der Abbau von isotaktischem und syndiotaktischem Polymethylmethacrylat, der mit statistischem Startschritt erfolgt, ebenso eine Abbruchsreaktion narh der 1. Ordnung zeigt. Auf Grund der hier gebrachten Ergebnisse, läßt sich die Verwirrung in der Literatur über die Aktivierungsenergien beim thermischen Abbau von Polymeth ylmethacrylat verstehen. Diese Energien hängen nicht nur von der Kettenlänge, sondern auch vom Mechanismus des Abbauprozesses, vom Umsetzungsgrad und vom Prozentsatz der Doppelbindungen am Kettenende ab.
    Notes: Rate constants of the thermal degradation of polymethylmethacrylate fractions have been measured over a range of temperatures, and the ARRHENIUS equations have been derived. There are two degradation reactions for this polymer; one “fast” reaction, which is chain-end initiated, due to double-bonded chain-end polymer molecules and one “slow” reaction, which is initiated at random. The energy of activation for the fast reaction is much smaller than that of the slow reaction. Both show two levels of energies of activation proceeding from long to short chains. These energies of activation increase with decreasing chain length of the polymer as expected from theory. Whereas the differences in energies for the fast reaction are in agreement with a mechanism consisting of chain-end initiation, depropagation, and second-order termination, a reasonable value for the overall energy for the slow reaction is only obtained for a first-order termination process. Such a reaction is not unlikely, as the polymer film contains appreciable amounts of monomer at this stage of degradation. The energies of activation for the slow reaction increase with percentage conversion as long as some double-bonded chain ends are still in the system. It has to be concluded that the degradation of isotactic and syndiotactic polymethylmethacrylate, which degrade by random initiation, also have a first-order termination reaction. On the basis of the results reported here, the confusion in the literature concerning energies of activation for the thermal degradation of polymethylmethacrylate can be understood. These energies do not only depend on chain length but also on the mechanism of the degradation process, range of conversion, and percentage of double-bonded chain ends in the system.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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