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  • Polymer and Materials Science  (6)
  • 1
    Electronic Resource
    Electronic Resource
    Mechanical shear degradation of polymers in solution by turbulent flow, 3Teil 2: cf.25.. The influence of chemical constitution and thermodynamic quality of the solvent on shear degradation (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 3545-3560 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mechanical shear degradation of polyisobutylene, polystyrene, poly(vinyl chloride), poly(methyl methacrylate), poly(decyl methacrylate), poly(methyl acrylate), and 1,4-polybutadiene in dilute solutions of tetrahydrofuran (THF) are studied under turbulent flow conditions through a capillary, in order to study the effect of the chemical constitution on shear degradation. In addition the influence of solvent quality on shear degradation is investigated. The changes of the molecular weight distribution curves were followed by gel permeation chromatography (GPC), in order to determine the degradation constants ki for the corresponding molecular weight distribution fractions M̄i. GPC calibration via the concept of universal calibration, Mark-Houwink relations for polyisobutylene, poly(methyl methacrylate), poly(methyl acrylate), 1,4-polybutadiene, and poly(dimethylsiloxane) in THF as solvent had to be established for this purpose. Substantial differences in the rate constants ki were observed as a function of M̄i, whereas a master curve resulted for all polymers except 1,4-polybutadiene when ki was plotted against the number of main chain carbon atoms n̄i for each molecular weight M̄i. From this the shear degradation of C—C single bond polymers can be represented by ki = C · n̄ia, C being independent of the chemical nature of the C—C single bond polymer, and a varying from 1,7 to 2,6. This means that in addition to the shape of the deformed macromolecule to be degraded not only its hydrodynamic volume (in rest) but also its chain length plays an important role. As to the influence of solvent quality, the degradation constants were found to increase with decreasing solvating power of the solvent. Mechanical shear degradation of the type discussed here takes place in drag reduction by polymers.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021821217
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 1. Kinetik, Molekulargewichtsabhängigkeit und Frage des Bruchmechanismus (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 513-528 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical shear degradation of poly(decyl methacrylate) with weight average molecular weights 1,0·106 ≤ M̄w ≤ 1,7·106, and molecular polydispersity ratio M̄w/M̄n = 5 in dilute solutions is studied in turbulent flow as a function of molecular weight using a special apparatus consisting of two vessels connected by a capillary. Shear stress and shear rate remained constant during degradation. The rate of degradation was followed up by molecular weight distribution curves using gel permeation chromatography and described by -dci/dt = ki·cn, i being a high molecular weight species of the distribution. The reaction was found to be of the first order (n = 1) independent of solvent and of capillary length. Rate constants ki in the molecular weight range from 3,2·106 to 13,5·106 proved to be proportional to the hydrodynamic volume of the polymer molecules expressed in terms of the product of intrinsic viscosity and molecular weight [η]i·Mi. This corresponds to a linear relationship between ki and Mi1,75. Additional experiments show that this type of dependence on molecular weight holds only for turbulent flow; in laminar flow the result of the literature could be confirmed that there is a linear relation between ki and Mi1. Both results are independent of capillary length. As to the mechanism of breakage in turbulent flow it seems that in one step each macromolecule is broken simultaneously into several smaller parts.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820219
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 2Teil 1: cf.12.. Die Abhängigkeit der Abbaugeschwindigkeit von der Polymergesamtkonzentration in guten Lösungsmitteln (1981)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 182 (1981), S. 529-547 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Mechanical shear degradation of poly(decyl methacrylate), (viscosity average molecular weight in tetrahydrofuran M̄η = 1,3·106, M̄w/M̄n = 5) in the thermodynamically good solvent tetrahydrofuran has been studied in turbulent flow through a capillary as a function of polymer concentration in the range from 0,22 to 8,9 g/100 cm3. Due to turbulent flow conditions the shear stress, shear rate and shear energy proved to be the same for all concentrations and remained constant during degradation, giving a general insight into mechanism of degradation. The rate of degradation has been followed using molecular weight distribution curves obtained by gel permeation chromatography. The reaction was found to be of first order. Rate constants determined for molecular weights from 3,2-9,5·106 decreased with increasing concentration following a law of the type ki = (K + b·c)-1, K and b being constants for each molecular weight. Hydrodynamic volumes of polymer molecules have been calculated according to models of Rudin as function of molecular weight and concentration. It can be shown that rate constants of degradation and calculated hydrodynamic volumes are proportional for the whole range of molecular weight and concentrations up to 3,6 g/100 cm3. There is also a rather good proportionality between these rate constants and the volumes of polymer coils predicted by de Gennes. This result is an additional confirmation of the concept that hydrodynamic volume governs shear degradation of polymer solutions. Additional experiments show that this type of concentration dependence is also to be found for other polymers in other solvents.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1981.021820220
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  • 4
    Electronic Resource
    Electronic Resource
    Zum abbau von polymerlösungen durch kapillarscherung. Einfluß der kapillarlänge und strömungsform auf den abbau (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 57 (1977), S. 99-109 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The dependence of shear degradation of polymer solutions on capillary length at constant shear stress is investigated with solutions of poly(isobutylene) (Mvis=6,1 · 106) in toluene. We examined concentrations of 0.1, 0.25, 1 and 4% and found the degradation to increase with capillary length. In 0,1% solution we found a decreased efficiency of degradation, due to a change in the structure of solution.Flow instabilities, which appear above a critical shear rate D in polymer solutions and pretend a loss in viscosity, are not caused by shear degradation. This result supports our interpretation of unstable flow of polymer solutions as slip flow (spurt).
    Notes: Der Einfluß der Kapillarlänge auf den Abbau von Polymerlösungen bei konstanter Schubspannung wird an Lösungen von Polyisobutylen (Mvis=6,1 · 106) in Toluol untersucht. Bei allen untersuchten Konzentrationen (0,1, 0,25, 1 und 4%) nimmt der Abbau mit steigender Kapillarlänge zu. Bei der 0,1proz. Lösung findet sich eine verringerte Effektivität des Abbaus, was auf eine Äderung der Lösungsstruktur zurückzuführen ist. Das oberhalb einer kritischen Scherrate D bei Polymerlösungen zu beobachtende instabile Fließen (scheinbare Viskositätsabnahme) ist nicht ursächlich auf Scherabbau zurückzuführen. Dieses Ergebnis ist eine indirekte Stütze für die Deutung dieser Fließerscheinung als Gleitfließen (spurt).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1977.050570108
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  • 5
    Electronic Resource
    Electronic Resource
    Die wirkungsweise der viskositätsindex-verbesserer (1978)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 67 (1978), S. 61-78 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: One of the major reasons for using polymeric additives is to obtain a product which has better viscosity-temperature characteristics than a comparable pure mineral oil. Extensive measurements of the viscosity-temperature behaviour of motor oils with and without polymer addition show the necessity of a revision of the generally accepted concept of the mechanism of viscosity index improvement. By addition of polymer the better viscosity-temperature characteristics of light oils, which are however of very limited value for lubrication of engines because of their low viscosity at high temperatures, can be maintained partially in the range of higher viscosities. So it becomes obvious how it is possible to produce multigrade oils both from polymers the polymer coil dimensions of which expand, as well as from polymers, the polymer coils of which contract with increasing temperature. In fact, coil expansion promotes viscosity index improvement to some extent but in no way does this effect play a decisive part.
    Notes: Durch Polymerzusatz hergestellte Motoröle besitzen gegenüber den mit ihnen konkurrierenden Einbereichsölenmit gleicher Viskosität bei derselben höheren Temperatur ein wesentlich verbessertes Viskositäts-Temperatur-Verhalten. Zur Frage der Wirkungsweise dieser Viskositätsindex-Verbesserer wurden ausführliche Messungen durchgeführt. Es zeigt sich, daß es durch Einsatz dieser Polymeren möglich ist, die von Natur aus günstigere Viskositäts-Temperatur-Charakteristik niederviskoser Grundöle, deren andere Viskositätslage von vornherein den praktischen Einsatz weitgehend ausschließt, tendenziell in das Gebiet höherer Viskosität „hinüberzuretten“. Die bisher wenigstens teilweise als entscheidend angesehene Frage der Polymerknäelexpansion erweist sich als Effekt zweiter Ordnung, der die Verbesserung des Viskositätsindex zusätzlich begünstigt, jedoch lassen sich Viskositätsindices ähnlicher Größenordnung auch durch Zusatz solcher Polymerer erreichen, bei denen mit steigender Temperatur keine Knäuelexpansion, sondern eine Knäelkontraktion zu beobachten ist.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1978.050670105
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanical shear degradation of a polymer solution by capillary flow (1980)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 1 (1980), S. 27-29 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1980.030010106
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