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  • 1
    Electronic Resource
    Electronic Resource
    Non-equilibrium contributions to the internal energy of PVAc melts (1980)
    Springer
    Rheologica acta 19 (1980), S. 482-487 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Deformationsversuche unter adiabatischen Bedingungen wurden als Test für das thermodynamische Verhalten von PVAc-Schmelzen im Nicht-Gleichgewichts-Zustand durchgeführt. Bei Temperaturen wenig oberhalb der GlastemperaturT g (d. h. 50°C und 60°C) wurde eine merkliche Abhängigkeit der Inneren Energie von der Deformationsvorgeschichte gefunden. Auf den NichtgleichgewichtsbeitragU entfällt bis zu 50% der Änderung der totalen Inneren Energie, und zwar kennzeichnet sie einen endothermen Effekt. Bei Anfahrversuchen zeigtU als Funktion der Scherung ein „Überschießen“. Während der adiabatischen Spannungsrelaxation wird ebenfalls eine „Temperatur-Relaxation“ beobachtet. Der Nicht-Gleichgewichts-Term der Inneren Energie wird bei 80°C vernachlässigbar gering, sowohl während der Deformation als auch der Spannungsrelaxation. Bei dieser Temperatur ist somit die Theorie der reinen Entropie-Elastizität anwendbar.
    Notes: Summary Adiabatic deformation experiments have been used as a test for the non-equilibrium thermodynamic behavior of PVAc melts. At temperatures slightly aboveT g (i.e. 50°C and 60°C), an appreciable dependance of internal energy upon deformation history is found. The non-equilibrium contributionU represents up to 50% of the total internal energy change and plays the role of an endothermic effect. In transient shear tests,U shows an overshoot with respect to deformation. During adiabatic stress relaxation a temperature “relaxation” is also observed. The nonequilibrium internal energy term becomes negligible at 80°C, both during deformation and stress relaxation. At that temperature, the entropic elasticity theory holds true.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01524021
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  • 2
    Electronic Resource
    Electronic Resource
    Testing of a constitutive equation for entangled networks by elongational and shear data of polymer melts (1973)
    Springer
    Rheologica acta 12 (1973), S. 269-275 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Summary An entangled network such as a polymer melt or a concentrated solution is here described by a set of two simultaneous equations. One of them is a balance of entanglements, the other gives the stress in the classical form of aMaxwell equation. The balance of entanglements contains both an entanglement generation term which depends on the “distance” from equilibrium and an entanglement destruction term which depends on the stress level. The parameters appearing in theMaxwell and the balance equations are made to depend in a specified way on the existing number of entanglements. The model is here tested by comparison with existing data of steady-state elongational and shear viscosity of polymer melts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01635115
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  • 3
    Electronic Resource
    Electronic Resource
    Thermodynamics of polymeric liquids: Simple fluids with entropic elasticity obeying the time-temperature superposition principle (1977)
    Springer
    Rheologica acta 16 (1977), S. 516-522 
    Details
    ISSN: 1435-1528
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zusammenfassung Polymerflüssigkeiten werden als einfache Flüssigkeiten betrachtet, welche die beiden folgenden Eigenschaften besitzen: 1. Sie unterliegen dem Zeit-Temperatur-Superpositions (TTS)-Prinzip; 2. sie sind mit Entropie-Elastizität ausgestattet. Es wird eine Analyse der bisher existierenden Theorien durchgeführt, welche diese Eigenschaften jeweils für sich betrachten. Dabei werden nicht-triviale Kompatibilitäts-Bedingungen gefunden, die wesentliche Abänderungen der Formulierung des TTS-Prinzips vonCrochet undNaghdi beinhalten. Die thermodynamischen Zustandsgleichungen von Flüssigkeiten, die sowohl dem TTS-Prinzip gehorchen als auch eine Konfigurations-Entropie besitzen, werden anschließend formuliert und diskutiert.
    Notes: Summary Polymeric liquids are considered to be simple fluids displaying two properties: i) they obey the time-temperature superposition (TTS) principle, and ii) are endowed with entropic elasticity. An analysis is performed of existing theories which consider the above properties separately. Non-trivial compatibility conditions are found, which require appreciable modifications of the formulation byCrochet andNaghdi of the TTS principle. The thermodynamic equations of state of fluids which obey the TTS principle and have a configurational entropy are then formulated and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01525650
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  • 4
    Electronic Resource
    Electronic Resource
    Transport of swelling penetrants in glassy polymers: Influence of convection (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 3627-3647 
    Details
    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 transport of a solute by diffusion into a glassy polymer can lead to swelling of the material. For certain types of polymers, a sharp interface is formed between the swollen region and the glassy core. When the density of the swollen material is much smaller than the density of the glass, a significant convective mass-average velocity is generated within the sample. Previous models have neglected the role this convection plays in solute transport and in the proper calculation of the sample dimensions as a function of time. In this paper, we study the contribution of convective terms to the solute transport process, including the motion of the swollen polymer/solution interface. We also compute the eulerian strains that result from the calculated velocity fields and the stresses that would be generated if a linear viscoelastic model is used as a constitutive equation relating the stress to the strain. We show that serious errors can be generated in the calculations if convective terms are neglected. Furthermore, a comparison of the strains and stresses acting on the polymer with those acting on the mixture of solute and polymer shows that they can be significantly different. The stresses and strains acting on the polymer alone offer the most rational physical picture of the material deformation.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070320219
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  • 5
    Electronic Resource
    Electronic Resource
    Chemical kinetics and diffusion in poly(butylene terephthalate) solid-state polycondensation: Experiments and theory (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 2873-2887 
    Details
    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: Postpolymerization was obtained in solid PBT sheets, by annealing in a dry nitrogen stream at 214°C. After different reaction times, the samples were cut into thin slices. The Mw profile within the sample was obtained through intrinsic viscosity measurements in a phenol-TCE mixture. At each location inside the sample, the [η] vs. time curve typically shows a maximum, which is rather broad at the midplane and much sharper at the external surface. The phenomenon was mathematically described by accounting for both diffusion and chemical reactions within the slab; five simultaneous chemical reactions have been considered. The observed behavior is found to be essentially due to two competing processes, i.e., the diffusion of the low molecular weight species generated during the polycondensation and the thermal degradation reaction. The model predictions are compared with the experimental data showing a satisfactory agreement.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070290917
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of the thermal histories on case II sorption kinetics: Test of a kinetic theory for swelling (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 4145-4159 
    Details
    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: Case II sorption kinetics have been analyzed for PS-n-hexane systems. Samples of polystyrene characterized by several different annealing histories were used. For all thermal histories, the n-hexane sorption kinetics at several temperatures were measured, as well as some relevant mechanical properties of the glassy matrix, e.g., density and initial stress for crazing. The main influence of the thermal history is to appreciably alter the initial stress for crazing σc, as well as the swelling kinetics. The σc curve vs. annealing time is seen to go through a minimum which is paralleled, at 40°C, by a maximum in the swelling kinetics. The independent mechanical and sorption data obtained were compared with a recently proposed [G. C. Sarti, Polymer, 20, 827 (1979); G. C. Sarti and A. Apicella, Polymer, 21, 1031 (1980)] theory for Case II kinetics, which is shown to be particularly suitable to describe the observed behavior.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291245
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  • 7
    Electronic Resource
    Electronic Resource
    A class of mathematical models for sorption of swelling solvents in glassy polymers (1978)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 18 (1978), S. 388-395 
    Details
    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: A class of mathematical models for sorption of swelling solvents in glassy polymers is analyzed. The essential features of these models are the explicit consideration of the kinetics of swelling and of the driving force for swelling. It is shown that, even when all other elementary phenomena are modeled in the simplest possible way, all the experimentally observed features of the processes considered are correctly predicted.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760180510
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  • 8
    Electronic Resource
    Electronic Resource
    Diffusion and localized swelling resistances in glassy polymers (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1018-1026 
    Details
    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: The sorption of swelling penetrants in glassy polymers is modeled as a diffusion problem with moving boundary. The velocity of the swelling front is related to the stress exerted by the penetrant on the glassy matrix at the moving boundary. The solvent stress is considered as the sum of the osmotic tension and of the differential swelling stress. The latter increases as the residual thickness of the glassy core is reduced, giving rise to an acceleration of the front velocity (Super Case II). It is shown that the stress relaxation properties in the swollen region must be taken into account in order to obtain a thickness-dependent Super Case II effect, which disappears in thick samples, according to experimental evidence. All the observed sorption behaviors, including Fickian diffusion, Case II, and Super Case II sorption, are properly accommodated in the theory.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221603
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  • 9
    Electronic Resource
    Electronic Resource
    Zero migration of monomers in glassy polymers: A possible artifact of thermal depolymerization (1983)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 23 (1983), S. 473-488 
    Details
    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: Efforts to remove traces of monomers contained in polymers by stripping with steam have resulted in reports that a small concentration of monomer is inextractable, or “locked-in,” the polymer. Any concomitant depolymerization to monomer and diffusive elution of the formed monomer would, in the steady state, result in a constant concentration of monomer within the confines of the polymer. If only the polymer phase were sampled and depolymerization were ignored, this result could be interpreted as an apparent “zero migration” level of monomer. A model that describes the coupled processes of depolymerization and diffusion is presented; predictions and estimates of an apparent “zero-migration” concentration are offered for various polymer/monomer systems considering a variety of kinetic schemes. The effects of temperature, geometry, and sample size on the transient and apparent steady-state, residual-weight fraction of monomer in the polymer are considered. Also, the weight fraction of monomer, neglecting diffusive elution, is estimated for comparison with the steady-state weight fractions calculated for the case in which diffusive elution significantly lowers the residual steady-state monomer level. The results predicted by the model presented are compared with experimental data reported in the literature. Transient approaches to the steady state are included in the model analysis. The steady-state monomer concentrations predicted for polystyrene and poly(acrylonitrile) at 100°C vary from 0.0001 ppm to 100 ppm as the diameter of the respective polymeric spheres varies between 0.5 μ and 500 μ. The predicted steady-state concentrations for vinyl chloride monomer in poly(vinyl chloride) are, under comparable conditions, seven orders of magnitude lower, reflecting the extraordinarily small tendency of polyvinyl chloride to degrade to monomer.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760230902
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  • 10
    Electronic Resource
    Electronic Resource
    Solubility, diffusivity, and mobility of n-pentane and ethanol in poly(1-trimethylsilyl-1-propyne) (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2245-2258 
    Details
    ISSN: 0887-6266
    Keywords: poly(1-trimethylsilyl-1-propyne) ; ethanol ; n-pentane ; solubility ; diffusivity ; mobility ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion coefficient of ethanol and of n-pentane in PTMSP, at 27°C, was measured as a function of concentration up to a penetrant content of about 12% by weight, for polymer samples obtained through different processes; differential sorptions and desorptions with vapor phases were considered. In the case of ethanol a nonmonotonous behavior was observed for the diffusivity, while in the case of n-pentane the same property was found to monotonously decrease with increasing the penetrant content. The sorption isotherms were also reported, indicating that n-pentane exhibits a typical dual mode behavior, while ethanol follows an unusual s-shape curve. The chemical potential of the dissolved penetrants, calculated directly from the isotherms, shows the very different importance of the energetic interactions of the two penetrants with the polymer units. In spite of the remarkably different concentration dependencies observed for both solubility and diffusivity of the two penetrants, the mobility factors are in both cases monotonously decreasing with the penetrant concentration, and follow very similar trends. The significant differences observed for the concentration dependence of the diffusion coefficients are, thus, associated to the thermodynamic contributions, which are very different for n-pentane and ethanol. Different polymeric films, obtained through different solvent evaporation processes, show quite different solubility, diffusivity and mobility for both ethanol and n-pentane. On the other hand, the ratio between the mobility of the two penetrants as well as the slope of mobility as function of the concentration remains the same for all the different samples inspected. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2245-2258, 1997
    Additional Material: 6 Ill.
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