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  • 1
    Electronic Resource
    Electronic Resource
    Creep measurements on “in situ” compatibilized polypropylene/polyamide-6 blends (1993)
    Springer
    Polymer bulletin 30 (1993), S. 603-608 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Rheological properties of Polypropylene/Polyamide-6 blends at different degrees of compatibilization were studied at 240°C. The compatibilizing agent was synthesized in situ during the mixing procedure. Creep measurements at constant stress levels were performed on a Rheometrics Stress Rheometer. The morphology of the blends was determined by scanning and transmission electron microscopy before and after the shear experiments. No changes of the morphology occurred during the experiments. In the creep experiments the flow zone was reached. Data of that region such as zero shear viscosity, creep compliance and terminal retardation time were determined. The values of these quantities increased with increasing amount of the compatibilizing agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296481
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  • 2
    Electronic Resource
    Electronic Resource
    Linear viscoelastic behaviour of complex polymeric materials: a fractional mode representation (1994)
    Springer
    Colloid & polymer science 272 (1994), S. 1536-1546 
    Details
    ISSN: 1435-1536
    Keywords: Rheological constitutive equation ; fractional derivatives ; material functions ; relaxation time spectra ; retardation time spectra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A rheological constitutive equation for complex polymeric materials is derived starting from a special formulation of the relaxation function. This relaxation function contains six parameters and is divided into three regions: the plateau region, an intermediate power-law region and the terminal region of rapid stress decay. Material functions like the complex modulusG * and the logarithmic density function of the relaxation time spectrum H and of the retardation time spectrum L respectively are derived. Material parameters like the zero shear viscosityη 0 and the equilibrium shear complianceJ e are also calculated. The comparison of the measured dynamic moduli of H-shaped polystyrenes, associating terminally functionalized polyisoprenes and randomly associating polybutadienes with the theoretical predictions of the proposed phenomenological model shows an excellent agreement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00664721
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  • 3
    Electronic Resource
    Electronic Resource
    Rheological analysis of triblock copolymer-microemulsion networks (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 568-575 
    Details
    ISSN: 1435-1536
    Keywords: Microemulsions ; networks ; blockcopolymers ; dynamics ; rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The rheological properties of microemulsion-triblock copolymer [poly(oxyethylene)-b-polyisoprene-b-poly(oxyethylene)] networks were studied by oscillatory shear measurements. The principal viscoelastic pattern of our systems stays the same whether the surfactant is ionic or nonionic. A closer examination shows, however, the enormous influence of the respective phase behavior of the underlying microemulsions. Also, specific interactions between the surfactants and the hydrophilic poly(oxyethylene) blocks lead to a significant effect on the formation of network structures. Characteristic rheological data such as plateau moduli and relaxation times for a series of different samples were derived differing in polymer or droplet concentrations, apart from the molecular weights of the poly-(oxyethylene) and the polyisoprene blocks. Finally, we could construct polymer and droplet concentration invariant master — mastercurves using the temperature invariant mastercurves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655232
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  • 4
    Electronic Resource
    Electronic Resource
    Generalized Cole-Cole behavior and its rheological relevance (1992)
    Springer
    Rheologica acta 31 (1992), S. 309-322 
    Details
    ISSN: 1435-1528
    Keywords: Linear-viscoelasticity ; material functions ; rheological constitutive equation ; fractional derivative
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Starting from an analysis of the rheological behavior of the complex modulus predicted by the Cole-Cole formalism, a generalized Cole-Cole ansatz is suggested in order to overcome the related difficulties. The corresponding rheological constitutive equation with fractional derivatives belonging to the generalized Cole-Cole respondance is stated and the characteristic material functions of the linear viscoelasticity theory (like the dynamic modulus and compliance, the relaxation and ratardation functions, the spectra, etc.) are derived. Model predictions of these functions will be compared with experimental results from dynamical measurements and creep data on different polymer systems which show cooperative phenomena (polymeric glasses and gelling systems). One can see that the modified ansatz fits the data very well, in spite of its relative simplicity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418328
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  • 5
    Electronic Resource
    Electronic Resource
    Nichtkorrekte Aufgaben in der Rheometrie (1983)
    Springer
    Rheologica acta 22 (1983), S. 425-434 
    Details
    ISSN: 1435-1528
    Keywords: Rheometry ; ill-posed problem ; method of regularization ; determination of relaxation functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Abstract The most important ill-posed problems in rheometry are discussed. One version of a regularization method (Tichonov-regularization), which gives stable solutions of such problems, is described. It is shown that the quality of the solution depends on the form of the stabilizing functional and on the quantity and the type of constraints. There are, however, no general rules for formulating the restrictions or selecting the performance criteria. The method is demonstrated for the determination of the relaxation function of several rheological models.
    Notes: Zusammenfassung Unter Verwendung des Begriffs der „nichtkorrekt gestellten Aufgabe“ wird eine theoretische Begründung für die schlechte Berechenbarkeit von Funktionen gegeben, die aus meßfehlerbehafteten Daten über die Lösung der inversen Aufgabe berechnet werden. Die wichtigsten nichtkorrekten Aufgaben der Rheometrie werden angegeben sowie die Variante eines Regularisierungsverfahrens (Tichonovsche Regularisierung) vorgestellt, die numerisch stabile Lösungen nichtkorrekter Aufgaben zuläßt. Dabei wird festgestellt, daß die Güte der Lösung u.a. von der Form des stabilisierenden Funktionals und der Anzahl sowie der Art der Nebenbedingungen beeinflußt wird, es aber keine allgemeinen Regeln zur Formulierung der Restriktionen oder der Auswahl des Gütekriteriums gibt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01462929
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  • 6
    Electronic Resource
    Electronic Resource
    Primary normal-stress coefficient prediction at high shear rates (1988)
    Springer
    Rheologica acta 27 (1988), S. 567-574 
    Details
    ISSN: 1435-1528
    Keywords: Material function ; normal-stress prediction ; mirror relation ; Kramers-Kronig relation ; polymersolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract On the basis of a brief analysis of well known normal-stress calculation methods, the necessity of improved models of prediction is elaborated. A modified form of the so-called mirror relation which meets these requirements is presented. In combination with the Carreau viscosity equation, an analytical solution is given which leads to a Carreau normal-stress coefficient equation and, thus, to a simple method of calculation. The comparison between measured normal stresses and those determined by experiments shows that the values calculated in accordance with the presented method agree well with the measured values, especially within the range of high shear rates. The parametersβ andK to be selected for this purpose are determined in dependence on the slope of the viscosity functionα 1 at high shear rates for each polymer individually, using empirical relations so that the global selection of parameters, which is common practice with other methods, is obviated. In an appendix a method for deriving the relations between material functions on the basis of operator calculation is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01337452
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  • 7
    Electronic Resource
    Electronic Resource
    A delta-function method for the n-th approximation of relaxation or retardation time spectrum from dynamic data (1991)
    Springer
    Rheologica acta 30 (1991), S. 7-13 
    Details
    ISSN: 1435-1528
    Keywords: Linear viscoelasticity ; complex modulus ; complex compliance ; relaxation and retardation spectrum ; approximative determination ; delta-function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A function series g(x; n, m) is presented that converges in the limiting case n→∞ and m = constant to the delta-function located at x = ωλ = 1. For every finite n, there exists 2n+1(−n≤m≤n) approximations of the delta-function δ(n)(x−x n,m ). x n,m is the argument where the function reaches its maximum. A formula for the calculation is given. The delta-function approximation is the starting point for the approximative determination of the logarithmic density function of the relaxation or retardation time spectrum. The n-th approximation of density functions based on components of the complex modulus (G*) or the complex compliance (J*) is given. It represents an easy differential operator of order n. This approach generalizes the results obtained by Schwarzl and Staverman, and Tschoegl. The symmetry properties of the approximations are explained by the symmetry properties of the function g(x; n, m). Therefore, the separate equations for each approximation given by Tschoegl can be subsumed in a single equation for G′ and G″, and in another for J′ and J″.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366789
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  • 8
    Electronic Resource
    Electronic Resource
    Rheology of nanocomposites based on layered silicates and polyamide-12 (2000)
    Springer
    Colloid & polymer science 278 (2000), S. 629-636 
    Details
    ISSN: 1435-1536
    Keywords: Key words Nanocomposites ; Polyamide ; Clay ; Rheology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Nanocomposites based on polyamide-12 (PA-12) and layered silicates are synthesized and analyzed with respect to their morphological and rheological properties. Transmission electron microscopy shows the fine dispersion of silicate layers in a PA-12 matrix. Different swelling agents for the clay (protonated aminododecanoic acid or water) are used. This allows the molar mass of PA-12 to be controlled during the preparation of the nanocomposites. When aminododecanoic acid is used as a swelling agent, the exfoliated silicate layers are chemically bonded to the matrix, whereas the use of water as a swelling agent leads to exfoliated silicate layers well dispersed in the polymer matrix without tethered polymer chains. The rheological behavior of the nanocomposites differs extremely from that of the pure PA-12 matrices. A qualitative description of the rheology of these nanocomposites is provided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960000294
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  • 9
    Electronic Resource
    Electronic Resource
    Deposition of PVD Coatings on different geometries and local characterization for reliable properties (1998)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 29 (1998), S. 72-76 
    Details
    ISSN: 0933-5137
    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
    Notes: Although the characteristics of PVD coatings in research and development papers are very promising, in the field of tribology the industrial application of these coating types is restricted to special market segments up to now: the deposition of hard coatings is state of the art on tools, whereas PVD coated machine components are quite rare.This is caused by the coatings profile of properties, the various surroundings and the demands for application reliability. The last aspect is the main topic of this contribution. Reliability is especially important for machine components, because tools may fail after relative short life time compared to machine parts. Besides this tools and the corresponding production equipment are designed for fast tool replacement in contrast to other machines, which should work without standstill and with a minimum of maintenance.Characteristics of coated systems must be guaranteed in practice theory and laboratory experiments have to show what is possible. On the one hand reproduction of the deposition process must be guaranteed to enter application fields with high demands for reliability, on the other hand characterization of coated systems must be standardized with admissible deviations for communication between coaters and users. These aspects are important for decisions concerning the use of coating substrate systems in tribology besides the topics of technical function.The present investigation shows main reasons for deviations in results of PVD coatings.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19980290211
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  • 10
    Electronic Resource
    Electronic Resource
    Lokale Schichterzeugung beim HF-Magnetronsputtern (1998)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 29 (1998), S. 452-458 
    Details
    ISSN: 0933-5137
    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: Local coating conditions in RF-Magnetron sputteringThe following paper illustrates the state of the art of the „RF-magnetron sputter technology“ for tribological applications. First the parameters to determine the results of deposition are presented and second a possible way of systematical engineering of coatings for tribological applications is discussed. Exemplary spots on different influencing variables are given. The macroscopic boundary conditions of the deposition unit and the objects to coat play a similar important role as the kinematic of threedimensional functional surfaces on the objects. Further more the substrat material (of the object to coat) as well as the load bearing capacity of the coated component in a special tribological application is of special importance. The presented measuring results are extracted from the quoted reference.
    Notes: Der folgende Artikel zeigt den Stand der Beschichtungstechnologie „HF-Magnetronsputtern“ für tribologische Anwendungen auf. Dabei wird zunächst dargestellt welche Parameter das Beschichtungsergebnis bestimmen und wie eine systematische Schichtentwicklung für tribologische Anwendungen aussehen kann. Im Einzelnen werden exemplarisch Einblicke in verschiedene Einflußparameter gegeben. Die makrogeometrischen Randbedingungen der Beschichtungsanlagen und Beschichtungsobjekte spielen dabei eine ebenso wichtige Rolle wie die Kinematik der Objekte mit dreidimensionalen, zu beschichtenden Funktionsflächen. Zusätzlich ist der Substratwerkstoff (Beschichtungsobjekt) wie auch letztlich das Beanspruchungsverhalten des zu beschichteten körpers im tribologischen Einsatz von zentraler Bedeutung. Die vorliegenden Meßergebnisse sind der angegebenen Publikation entnommen.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19980290903
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