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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Macromolecules 9 (1976), S. 76-80 
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 74 (1952), S. 195-200 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 55 (1951), S. 1512-1527 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    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: To obtain accurate measurements of the limiting viscosity number (LVN) or the intrinsic viscosity [η] of solutions of ultrahigh molecular weight polyethylene (UHMWPE), a low shear floating-rotor viscometer of the Zimm-Crothers type was constructed to measure viscosities at elevated temperatures (135°C) and near zero shear rate. The zero shear rate measurements for UHMWPE whole polymer and UHMWPE fractionated by hydrodynamic crystallization were compared with viscosity measurements at moderate and high shear rates (up to 2000 s-1) carried out in a capillary viscometer. The limiting viscosity number of UHMWPE decreases, as expected, with shear rate. The higher shear rate data could not be extrapolated to yield the correct zero-shear rate viscosities. Fractionation of UHMWPE gave 10 fractions ranging in LVN from 9 to 50 dL/g. A tentative integral molecular weight distribution for the whole polymer was calculated on the basis of the Mark-Houwink equation, but because it had been previously established only for lower molecular weight polyethylenes, it may not be accurate. A correlation was found between the LVNs for the fractions in the two types of viscometers.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 1763-1776 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: As in the case with other polymers previously reported, the values of the refractive index increment dn/dc of polyethylene and the n-alkanes change with molecular weight. Most of the variation may be understood by examination of the role of density in the Lorentz-Lorenz mixing equation for specific refractivity, R12 = p1R1 + P2R2 used to calculate dn/dc. It may also be shown that as the absolute refractive index difference between solute and solvent becomes smaller, dn/dc becomes more sensitive to density change of the solute.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 2 (1962), S. 222-226 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Using a high shear rate capillary viscometer, the melt viscosities of a series of high density linear polyethylenes ranging in weight average molecular weight from 70,000 to 160,000 have been measured from shear rates of 2 to 200 sec-1 and from 190° to 240°C. The data, corrected for elastic end effects are described by an empirical relationship except for the temperature term which is fitted to the Williams-Landel-Ferry equation. Over the range measured the viscosity is given approximately by a power law in relation to shear rate with an exponent dependent upon molecular weight.The effects of distribution were examined by measuring the viscosity-shear rate relationships for not only the above series, which varied in Mw/Mn from 23 to 10, but also for blends of polyethylenes of varying molecular weights or of fractions, and other polyethylenes obtained by removal of the high molecular weight tail. In general, the broader the distribution, the more sensitive is the viscosity to the rate of shear.The end correction, a measure of the elastic energy, does not vary much with shear stress or temperature in the case of high density polyethylene.
    Additional Material: 10 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 81 (1965), S. 14-31 
    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: Ein Verfahren zur Bestimmung von Gewichts- und Zahlenmittel des Molekulargewicht von Trioxancopolymeren mit geringem Gehalt an Oxyäthylenbausteinen wurde mit Hilfe von Lichtstreuung und osmotischen Messungen entwickelt. In guter Übereinstimmung mit indirekten Schätzungen über den Effekt von Kettenüberträgern wurde das Verhältnis Mw/Mn für eine Anzahl unfranktionierter Polymerer zu ungefähr 2 bestimmt. Ferner wurden Viskositätsmessungen in verdünnter Lösung und in der Schmelze ausgeführt. Die Schmelzviskosität bei der Schergeschwindigkeit Null ist für einfache Polymere und für Mischungen zweier Polymere ungefähr proportional zu Mw3,4. Die Abhängigkeit der Schmelzviskosität von der Schergeschwindigkeit gehorcht der empirischen BUECHE-HARDING-Gleichung; aber die Werte für MR, die sich mittels dieser Gleichung berechnen lassen, sind viel Kleiner als Mw. In Mischungen sind die MR-Werte größer als diejenigen der Komponenten. Alle Ergebnisse stehen in Übereinstimmung mit Messungen an anderen Polymeren, welche ungefähr dieselbe Molekulargewichtsverteilung besitzen.
    Notes: Methods have been developed for the determination of weight and number average molecular weights of copolymers of trioxane containing oxyethylene units by light scattering and osmotic pressure measurements, respectively. The ratio Mw/Mn for a number of whole polymers is close to 2, in good agreement with the estimate of this ratio indirectly determined from the effect of chain transfer agent. Dilute solution and melt viscosity measurements have also been made. The melt viscosity at zero shear rate is approximately proportional to the 3.4 power of Mw, both for polymers as polymerized and for a blend of two such polymers. The dependence of melt viscosity on shear rate can be fitted to the BUECHE-HARDING emperical equation, but the values of MR calculated from this equation are much smaller than Mw. For the blend MR is higher than that of either component. All of the results are in accord with those found for other polymers of about the same molecular weight distribution.
    Additional Material: 12 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 13 (1969), S. 961-975 
    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: The tensile stress-strain behavior of glass fiber-reinforced polyacetal resin was investigated for various fiber concentrations, fiber length distributions, and finishing agents. The polyacetal fiber blends change considerably in strength and elongation at break when treated with ammonium chloride, but otherwise similar specimens still follow a common stress-strain curve to a point shortly before failure. As the mean fiber length decreases, the modulus and tensile strength fall, but the elongation at break remains almost unchanged. The observed tensile behavior is discussed in terms of a simplified model, which assigns the fibers to two categories: a fraction α parallel to the applied load, and the remainder distributed in a plane perpendicular to the load axis. By fitting this model to the stress-strain curves, two other constants of each system are derived: a length-dependent efficiency factor β for parallel fibers, whose magnitude agrees with the predictions of Rosen and his co-workers, and a factor γ which expresses the constraint of the matrix resin by the “transverse” fibers. The behavior of γ is consistent with Tsai's theory of the transverse modulus of laminates, if a reasonable amount of fiber-fiber contact is assumed. In terms of this model, possible interpretations of the behavior under repeated loading and the mechanism of tensile failure are presented.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 13 (1979), S. 821-824 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Additional Material: 2 Ill.
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  • 10
    Publication Date: 1976-01-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
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