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  • Chemistry  (27)
  • Wiley-Blackwell  (27)
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  • Wiley-Blackwell  (27)
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  • 1
    Electronic Resource
    Electronic Resource
    The solid polymeric state: Thermodynamic and relaxational aspects (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 2 (1979), S. 143-154 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The statistical thermodynamics of the melt and the crystal are discussed by a unified approach which distinguishes between the two phases only in terms of a structure function minimizing the configurational free energy. The ensuing equations of state at atmospheric and elevated pressures are compared with typical experimental data for polymer and oligomer melts, and crystalline as well as semicrystalline systems, with satisfactory results. As to the glassy state, expansivity data clearly reflect nmot only the glass transition, but also sub-glass relaxation processes. In the spirit of the preceding discussion of the equilibrium melt, quasi-thermodynamic conditions are considered. Here the non-equilibrium character is reflected in the dependence of the extensive thermodynamic functions on thermal history in addition to the ambient variables of state. This state is discussed in terms of modifications of the liquid state model.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.020021979109
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  • 2
    Electronic Resource
    Electronic Resource
    Some considerations on equation of state and phase relations: Polymer solutions and blends (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1654-1664 
    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: We review briefly the general assumptions underlying hole theories of the configurational thermodynamic functions for single and multiconstituent systems. From the original Simha-Somcynsky theory several important modifications have recently evolved. First, there is a revision of the combinatorial entropy originating from the mixing of segments and holes in the spirit of Huggins's theory. With consistent additional modifications of the configurational free energy, quantitatively significant consequences for certain aspects of phase equilibria can arise. Finally, allowance for nonrandom mixing of constituents species and holes has been made. We illustrate the theory's potentials first in terms of pressure-volume-temperature (PVT) data for high and low molar mass species and their miscible mixtures. The influence of PVT properties on the miscibility behavior of solutions and blends is examined next. Of particular concern are the connections between predictability of lower from upper mixing spinodals, pressure effects, and the binary interaction χ-function.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760322203
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  • 3
    Electronic Resource
    Electronic Resource
    Free volume, hole theory and thermal properties (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 2645-2651 
    Details
    ISSN: 0887-6266
    Keywords: van der Waals free volume ; hole theory ; thermal properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Free volume ideas have been employed extensively in the interpretation of equilibrium processes and as a measure of molecular mobility. More recently, the vacancy fraction h, defined in our hole theory, has served to provide a link between diverse processes. This raises a question regarding the relation between the van der Waals type of free volume and h. As an important and useful result, valid for polymers and low molar mass fluids, simple relations are obtained between the van der Waals volume Vw, computed according to Bondi's structural rules, and the scaling volume V* in the hole theory. This is defined by the intersegmental potential and extracted from the equation of state. In turn, this result enables us to compute the corresponding scaling temperature T*. In this manner the theory predicts the volume-temperature function for a melt, based on a single experimental datum. Corresponding considerations are presented for the glassy state. The quantitative relation between the van der Waals type of free volume vf and h derived makes it possible to reconsider various empirical correlations involving the former. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090321610
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  • 4
    Electronic Resource
    Electronic Resource
    PVT scaling parameters for polymer melts (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 37 (1989), S. 2603-2616 
    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: Scaling parameters for two PVT equations of state are evaluated for 11 polymer melt systems using a nonlinear least square fitting algorithm that analyzes all of the experimental data simultaneously. Two different criteria are considered in this evaluation. In the first method, the fitting criterion is the difference between the calculated and experimental volume. In the second method, the criterion is the difference between the calculated and experimental pressure. In both cases, the differences between the scaling parameters obtained using the simultaneous fit procedure and those obtained using the earlier consecutive fit procedure are a few percent, which can have a significant effect in some calculations. In addition to being a more consistent method of evaluating scaling parameters, the simultaneous fit procedure leads to much better agreement between calculated and experimental values, in some cases by a factor of 2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070370912
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  • 5
    Electronic Resource
    Electronic Resource
    Equation of state of cis-1,4-polybutadiene melt (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 845-848 
    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: Recent equation of state data are analyzed in terms of the hole theory of polymer melts. The good agreement between experimental and theoretical volume-temperature curves at atmospheric pressure, observed previously for a number of amorphous and crystallizable polymers, is again confirmed. Similarly, satisfactory theoretical results for the isotherms ensue, with deviations however becoming noticeable at elevated pressures and low temperatures. The linearity of the isochores observed experimentally is confirmed by the theory, however with somewhat different slopes. Departures of maximally 10 percent from the thermal pressure coefficients derived from the experimental PVT data are noted. Significant differences between theory and experiment apper only in the third derivatives of the partition function, as has also been observed with other pollymers. The characteristic scaling parameters of volume, temperature and pressure show the expected similarity with hevea rubber. Earlier correlations for scaling entropy and segmental volume with scaling temperature are found to be valid within the scatter of these relations. Finally, the applicability of the empirical Tait equation in the form applied to the equation of state in other polymer melts is confirmed. Although the resulting thermal pressure coefficient exhibits an explicit even if smal dependence on temperature, in disagreement with experiment or theory, the Tait equation remains a useful relation for the representation of PVT information.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760191206
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  • 6
    Electronic Resource
    Electronic Resource
    Statistical thermodynamics of blends: Equation of state and phase relations (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1284-1290 
    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: We discuss the free-energy expressions for homogeneous melts and their blends, based on our hole theory. Equation of state (PVT) and free energy of mixing (ΔGm) are considered from a common point of view without the introduction of additional parameters to pass from the first to the second set of properties. Practical problems arise from the fact that ΔGm represents a difference between large quantities. As illustrations we analyze two typical systems. One is the n - C6 + n - C16 pair where PVT and ΔGm, the latter at atmospheric pressure only, have been studied experimentally. The other is n - C6 with a low and high molecular weight respectively of polyethylene as solute. Here the PVT relations of the components only are known. The effects of intercomponent attractions, temperature, pressure, and molecular weight on phase behavior are investigated. Critical coordinates, lower critical-solution temperatures (LCST) and their pressure dependence are computed. An iso-free volume condition obtains for this dependence where free volume is defined by the hole fraction inherent in the theory. Comparisons with experimental observations and other theoretical computations for different molecular weights are limited by the effect of polydispersity. Moreover, cloud point curves are shown. We finally compute the composition and pressure dependence of the χ-parameter which is implicit in the theory. We conclude with some comments regarding polymer blends.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241703
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular dynamics of physical aging in the glassy state (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1071-1078 
    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: We review first recent results concerning the relation between the relaxation of extensive thermodynamic and of viscoelastic functions. In the underlying theory a central role is assigned to a particular excess-free volume function h. It was originally introduced in a theory of the equilibrium melt. The time dependence of h can then be derived from volume (or enthalpy) recovery data and serves to predict other quantities, such as mean-square density fluctuations and viscoelastic-temperature shift factors during the aging process. Next the physical basis and results of two kinetic theories of volume relaxation are summarized. In both approaches the h-function is employed as an expression of the molecular dynamics in the drive to equilibrium. The first describes a gradual elimination of free-volume gradients through a diffusion process, characterized by a diffusion parameter, varying with the local free volume in accord with a Doolittle relation. The second, a stochastic theory, derives expressions for the matrix of transition rates between different free-volume states, the resulting spectrum of retardation times, and the size distribution of free volume in the relaxing system. Satisfactory agreement between observed and predicted volume recovery of poly(vinyl acetate) ensues. In the limit of an infinitesimal temperature jump, both theories yield a Williams-Watts correlation function as an approximate interpolation expression. The exponent β, however, varies in time with a constant value of approximately 0.60 over a limited time interval.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241402
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  • 8
    Electronic Resource
    Electronic Resource
    Transitions, relaxations, and thermodynamics in the glassy state (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 82-86 
    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 PVT properties of polymer glasses are discussed from two points of view. First, as a low frequency tool in the study of sub-glass relaxations. Dilatometric results illustrate the sensitivity of the thermal expansivity and its temperature coefficient to dynamic processes occuring in the glass. The second point of view considers the quasi-thermodynamics of the non-equilibrium system, under conditions where the rates of relaxational processes are small in comparison with experimental rates, and time dependent processes are practically absent. The starting point is a theory of the equilibrium melt which describes the characteristic liquid disorder in terms of a temperature and pressure dependent hole or loosely, free volume fraction. This function is obtained by the minimization of a configurational free energy. Upon reaching the glass transition, this dependence is reduced, and further so in a sub-glass relaxation region. However, it is not eliminated until temperatures of the order of 50 to 70 K are reached. While this picture is qualitatively universal, significant quantitative differences are observed with different chemical structures and different thermal and pressure histories. A comparison of thermal expansivities of high and low Tg systems indicates that in the former the free volume retained upon reaching Tg is comparatively large and the departure from equilibrium or degree of freeze-in comparatively small. Similarly, it appears that the glassy densification generated by cooling the melt under pressure is more extensive in high Tg glasses. Such results imply structural differences. These should be investigated by comparative studies of (a) time dependent processes in terms of the free volume functions, (b) sorption and transport, and (c) the temperature dependent dynamics of density fluctuations.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200114
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  • 9
    Electronic Resource
    Electronic Resource
    PVT scaling parameters for polymer melts. II. Error in all variables (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 983-991 
    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: An algorithm is discussed for determining best-fit scaling parameters in the PVT equation of state of polymer melts from experimental data. The underlying theoretical expressions are those employed in our preceding work. There it was assumed that values of pressure and temperature are known exactly and experimental uncertainty was admitted in the volume solely. This condition is now relaxed to allow for errors in P and T also. The methodology developed involves multiple small nonlinear fitting problems for two or three unknowns at a time. We employ it on the experimental data base in the earlier work, which consists of 11 polymer melts. To these is added ethylene monomer, analyzed earlier by Nies et al. by different methods. The numerical values of the scaling parameters differ by at most a fraction of a percent from those in the earlier computations and enhance the accuracy of fit but slightly. The significant improvement over the consecutive procedure (analysis of atmospheric pressure isobar, followed by isotherms at elevated pressures), seen earlier, continues therefore. The scaling parameters so obtained should represent the ultimate in computational accuracy consistent with a specified experimental accuracy. This may have a bearing ultimately on the issue of modeling molecular characteristics, expressed through the scaling parameters, versus macroscopic properties. Using the parameters determined here, it is shown that the entropy is correlated with the scaling temperature and that the flexibility parameter is related to polymer complexity.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430516
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  • 10
    Electronic Resource
    Electronic Resource
    Low-temperature thermal expansivities of polyethylene, polypropylene, mixtures of polyethylene and polypropylene, and polystyrene (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1455-1473 
    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: Length-temperature measurements on a series of polymer blends over the whole range of composition from pure polyethylene to pure polypropylene and one set of determinations on a 50:50 copolymer and on polystyrene are evaluated. The total crystallinity of the samples did not exceed 54%. The experimental procedure utilized a linear variable differential transformer without the use of a confining fluid, and the temperature ranged from about +20 to -185°C. A least-square numerical differentiation procedure based on moving arcs is applied to yield directly the coefficients of thermal expansion as a function of temperature. The linear voltage differential transformer (LVDT) technique can detect transitions in which the change in thermal expansion coefficients is less than 10-5°C.-1. In polypropylene as well as the blends, the principal glass transition is clearly seen in the range observed by others, namely at about -9 to -14°C. Its location varies only slightly with composition at polyethylene contents less than 88 mole-%. For polyethylene the transition region broadens noticeably. The results are suggestive of two transitions for 0 〉 T 〉 -40°C. A second transition region is observed for either pure component around -126°C. Its location varies some what with composition. However, our results do not indicate the appearance of an additional transition region characteristic of the mixture. The copolymer exhibits a major transition at -61°C. in good agreement with earlier workers. The thermal expansion decreases again around -150°C. In general our observations concerning transitions below Tg are consistent with dynamic results.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070101006
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