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  • Polymer and Materials Science  (31)
  • GENERAL  (2)
  • 1975-1979
  • 1955-1959  (33)
  • 1957  (33)
  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 23 (1957), S. 233-240 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Dielectric properties and loss factors have been measured for dilute solutions of polyvinyl chloride in tetrahydrofuran and mixtures of this solvent with heptane, for solutions of polymethyl methacrylate in benzene and toluene, and for solutions of polyvinyl acetate in toluene. Concentrations varied from 0.5 to 8 g./100 ml. Frequencies ranged from 0.01 to 35 megacycles/sec., and temperatures from -35° to +25°C.Only one sample of polyvinyl chloride was used (DP = 1,750), but six fractions of methyl polymethacrylate (DP = 240 - 12,500) and four of polyvinyl acetate (DP = 2,550-23,250). Numerical values for the three polymers were rather similar. The root mean square dipole moments were proportional to the square root of DP. Relaxation times were practically independent of DP.
    Notes: Les propriétés diélectriques et les facteurs de perte ont été mesurés pour des solutions diluées de chlorure de polyvinyle dans le tétrahydrofurane et des mélanges de ce solvant avec l'heptane, pour des solutions de polyméthacrylate de méthyle dans le benzène et le toluène, et pour des solutions d'acétate de polyvinyle dans le toluène. Les concentrations variaient de 0.5 à 8 g./100 ml. Les fréquences allaient de 0.01 à 35 mégacycles/sec. et les température de -35° à +25°C. Un seul échantillon de chlorure de polyvinyle a été utilisé (DP = 1750); par contre quatre fractions de polyméthacrylate de méthyle (DP = 240-12.500) et quatre d'acétate de polyvinyle (DP = 2.550-23.250) ont été utilisées. Les valeurs numériques des trois polymères étaient plutǒt similaires. Les moments dipolaires moyens étaient proportionnels à la carrée du DP. Les temps de rélaxation étaient pratiquement indépendants du DP.
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  • 2
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Sress corrosion in homogeneous alloys, its conditions and its mechanismAt first the kinds of alloys showing the optimum initial conditions for an investigation of stress corrosion are discussed. According to the author's opinion homogeneous, not supersaturated, binary mixed crystalls of very noble components will be suitable (e.g. CuAg, AgAu, etc.)The occurence of stress corrosions is dependent on the following conditions: 1. characteristic susceptibility of an alloy to stress corrosion. 2. chemical action of a corroding atent at least upon the less noble constituent of the alloy. 3. tensile stress. These problems have been made subjects of exhasutive investigations.The most important factor influencing the suceptibility of homogeneous mixed crystalls to stress corrosion cracking is the amount of the mixed crystall concentration. About this series of exhaustive experiments as well as of analogous experiments under the influence of mercury were carried out. The result is that the reactivity of the gret angle grain bundaries as well as of the glide planes will be increased considerably with increasing mixed crystall concentration and will reach its maximum at 50 atom percent. so a new “mixed crystall effect” was found which is the chief cause of the suceptibility of homogenous mixed crystalls to stress corrosion.Further reslts are that under the inluence of chemical agents the mixed crystall effect will only be noticeable if the attack is supported by an electochemical process. Investigations showed that during the attack on homogeneous mixed crystalls electrochemical processes might occur if the basic metal is less noble than the alloyed constituent. Tis explains the peculiar course of the susceptibility to stress corrosion in dependence of the mixed crystall concentration which does not correspond to the alteration of the reactivity.Finally exhaustive investigations on the effect of tensile stress were carried out. Tensile stress was found to be effective only if it causes local, plastic deformation. So a considerable increase of reactivity will take place in statu deformandi only. The increase depends on the concentration of mixed crystalls as well and will reacgh its maximum at 50 atom percent.Then the causes of the occurence of inter- resp. transcristalline cracking in cubic face centered mixed crystalls are discussed. From the obtained results a conception of the mechanism of the formation of inter- and transcristalline cracking is developed.
    Notes: Es wird zunächst die rage diskutiert, welche Art von Legierungen die günstigsten Ausgangsbedingungen für eine Erfassung der Ursachen der Spannungskorrosion aufweisen. Dies sind nach Ansicht des Verfassers homogene, nicht übersättigte binär Mischkristalle aus möglichst edlen Komponenten (z. B. CuAu, AgAu u. a.)Für das Auftreten von Spannungskorrosion müssen bekanntlich folgende Voraussetzungen erfüllt sein: 1. Spannungskorrosions-Empfindlichkeit der Legierung; 2. Einwirkung eines chemischen Agens, das wenigstens die unedlere Komponente der Legierung angreift; 3. Vorhandensein mechanischer Zugspannungen. Über diese 3 Punkte werden eingehende Untersuchungen angestellt.Als wichtigster Faktor, der die Spannungskorrosions-Empfindlichkeit homogener Mischkristalle beeinflußt, erweist sch die Höhe der Mischkristallkonzentration. Hierüber werden eingehende Untersuchungen durchgeführt, die durch analoge Untersuchungen unter Einwirkung von Quecksilber ergänzt werden. Diese führten zu der Erkenntnis, daß das Reaktionsvermögen der Großwinkel-Korngrenzen wie auch der Gleitbereiche mit zunehmender Mischkristallkonzentration ganz beträchtlich erhöht wird und bei 50 At-% ein Maximum erreicht. Damit wurde ein neuer „Mischkristall-Effekt“ erfaßt, der die Hauptursache für die Spannungskorrosionsempfindlichkeit homogener Mischkristalle darstellt.Ferner ergab sich, daß sich der „Mischkristall-Effekt“ bei Einwirkung chemischer Agentien im allgemeinen nur dann bemerkbar macht, wenn der Angriff durch einen elektrochemischen Prozeß unterstützt wird. Untersuchungen hierüber legten klar, daß auch bei homogenen Mischkristallen während des Abbaues derselben ein elektrochemischer Prozeß auftreten kann, allerdings nur dann, wenn das Basismetall unedler ist als die zulegierte Komponente. Damit erklärt sich der eigentümliche Verlauf der Spannungskorrosionsempfindlichkeit in Abhängigkeit von der Mischkristallkonzentration, der sich nicht mit der Änderung des Reaktionsvermögens deckt.Eingehende Untersuchungen wurden schließlich noch über die Wirkung der Zugspannungen ausgeführt. Wie sich ergab, sind sie nur dann wirksam, wenn sie ein örtliches plastisches Fließen hervorrufen. Es tritt demnach nur „in statu deformandi“ eine beträchtliche Reaktionssteigerung auf, die ebenfalls von der Mischkristallkonzentration abhängt und bei 50 At-% ihren Höchstwert erreicht.Es wird dann noch die Ursache für das Auftreten inter- bzw. transkristalliner Risse bei kubisch-flächenzentrierten Mischkristallen behandelt und abschließend eine aus den hier gewonnenen Ergebnissen resultierende Vorstellung über den Mechanismus der inter- und transkristallinen Rißbildung entwickelt.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 24 (1957), S. 1-9 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Viscometric data obtained over a temperature range of 0-150°C. for a series of salicyloxymethyldimethyl end-blocked dimethylpolysiloxane fluids have shown that the molecular weight at which a minimum viscosity is exhibited is temperature-dependent. Thus, with decreasing temperature, minimum viscosities were manifested at higher molecular weights. With increasing molecular weight, i.e., increasing siloxane character, the energy of activation of viscous flor (Evisc) not only decreases, but also is less temperature dependent. An empirical expression relating Evisc and temperature for such fluids is presented.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 23 (1957), S. 297-314 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling in various liquids of discs of nylon 66, crosslinked by the radiation from an atomic pile, has been interpreted using the Flory-Rehner treatment of the swelling of cross-linked networks. Values of χ1, the polymer-solvent interaction parameter, found in this way have been discussed in terms of the physical properties of the liquids. The solvent power of about twenty phenols can be correlated with their known ability to form hydrogen bonds. Intramolecular bonding, as in guaiacol or o-chlorophenol, reduces the solvent power. Partially hindered phenols, i.e., those with one bulky hydrocarbon group ortho to the hydroxyl, show high solvent power, probably because polymer-solvent interaction is not hindered sterically as much as solvent-solvent interaction. Other classes of solvents, e.g., inorganic and organic acids, inorganic salts in hydroxylic solvents, are also discussed briefly. Some implications of these results in such technological fields as plasticizers and dyeing assistants are suggested.
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  • 5
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization characteristics of six different fluorinated olefin oxides have been studied. The initial effort in this work was on the homopolymerization of 1,1,1-trifluoro-2,3-butylene oxide. Attempts to polymerize this material have been made by mass polymerization over a broad temperature range using a number of different compounds as potential polymerization catalysts. Among these compounds were FeCl3, FeCl3 · 6H2O, AlCl3, a BF3-etherate complex, KOH, gamma radiation from a cobalt-60 source, a heterogeneous catalyst formed from aluminum triethyl and TiCl4, and a FeCl3-propylene oxide complex. All of the polymeric products obtained from these experiments were liquids of a relatively low molecular weight. The highest molecular weight polymers were obtained using FeCl3, AlCl3, and BF3. An attempt was subsequently made to determine the relative polymerizability of other, more highly substituted, fluorinated olefin oxides. These were 1,1,1-trifluoro-2,3-pentylene oxide, 1,1,1-trifluoro-2,3-isopentylene oxide, 1,1,1,2,2,3,3-heptafluoro-4,5-hexylene oxide, 1,1,1,-2,2,3,3-heptafluoro-4,5-heptylene oxide, and 1,1,1,2,2,3,3-heptafluoro-4,5-isoheptylene oxide. FeCl3 and AlCl3 were found to be effective catalysts for the mass polymerization of these materials to form liquid polymers. It was observed that the tendency to polymerize decreases in this group of compounds as the amount and complexity of substitution on the ethylene oxide nuclcus increases. All of these monomers are less reactive toward polymerization than is trifluorobutylene oxide; as a result, lower molecular weight products were formed in lower yields.
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 24 (1957), S. 333-348 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular weights of low pressure polyethylene fractions were measured by an ebulliometric method and an osmotic pressure method. The results can be correlated by an equation, [η] = 5.10 × 10-4 M0.725, with the intrinsic viscosity measured at 130°C. in Tetralin, for a molecular weight greater than 3750. All three types of polymer fractions, Ziegler-type low pressure polyethylene, Phillips low pressure polyethylene, and polymethylene from the decomposition of diazomethane, conform to the above correlation. The molecular weight distributions of two samples of Ziegler type polyethylene and one sample of Phillips' Marlex 50 were determined. All three distributions were found to be very broad and contained large amounts of low molecular weight materials.
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  • 7
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two viscometric methods have been developed for detecting the “critical concentration” (the concentration at which individual polymer molecules interfere with each other) of a dilute solution of a high polymer, B. In the first of these, the intrinsic viscosity, [η], of another polymer, A, is measured in a series of mixed solvents, each consisting of a solution of Polymer B in the solvent S, and each differing from the others only in the concentration of B (CB). For a number of polymer-polymer-solvent systems, data are presented which show that [η] is essentially independent of CB, except over a small range where its value changes fairly abruptly. This change marks the critical concentration. The second method is much faster but probably less reliable than the first. Nevertheless, the two gave values in good agreement. A method of calculating the critical concentration, based on the Flory-Fox theory of intrinsic viscosity, is described. Critical concentrations calculated for the several systems investigated agreed well with those obtained experimentally. The critical concentration was shown to be inversely proportional to the intrinsic viscosity of the Polymer B in experiments in which [η]B was varied by changing the molecular weight of the polymer and by changing the solvent. The effects observed are explained as resulting from interactions of the two polymer species in the solutions.
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 24 (1957), S. 439-443 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is shown that the direct photopolymerization of pure vinyl chloride in bulk shows a “gel effect,” i.e., a long period of accelerating rate at the beginning of the reaction. Cyclohexanone acts as both a solvent for the polymer and a photosensitizer for the polymerization. The mechanism of initiation by cyclohexanone is discussed; it is by no means certain that diradicals are formed.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 25 (1957), S. 115-117 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 23 (1957), S. 635-650 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Specimens of sodium alginate have been investigated dielectrically in aqueous solution at low concentrations. The effect on the dielectric increment and dispersion of concentration of polyions and counterions, isoionic dilution, degree of polymerization and degree of neutralization of polyions, and the dielectric constant of the solvent has been studied mainly. Qualitative interpretation of the data in accordance with the present polyelectrolyte theory as Maxwell-Wagner or Debye-Falkenhagen effects has been attempted.
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