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  • 1
    Electronic Resource
    Electronic Resource
    Onset of phase separation in segmented urethane polymerization (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 2067-2076 
    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 development of heterogeneous structure during the polymerization of a polyurethane system using a polyether diol of M̄n = 2000 as the soft segment and 4,4′-diphenylmethane disocyanate extended with 1,4-butanediol as the hard segment was monitored following the amount of light transmitted by the sample and the increase in viscosity of the reacting mixture. The amount of light transmitted by the reacting sample was observed to decrease sharply at a given point in the reaction. The cloud point was taken as the onset of phase separation in the system and the number average sequence at this point was found to be fairly constant at about 1.3 independent of reaction temperature and system composition. In many cases, the cloud point occurred at quite low conversion, meaning that a significant amount of subsequent polymerization occurs in a heterogeneous medium. It was also found that the viscosity of the material reached very large values at partial conversions of the monomers and presented throughout the reaction values larger than those expected from an increase in molecular weight alone. Viscosity is apparently sensitive to a different aspect of the phase separation process than the light transmission.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1981.070260628
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  • 2
    Electronic Resource
    Electronic Resource
    Consistent values of rate parameters in free radical polymerization systems (1988)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 26 (1988), S. 293-297 
    Details
    ISSN: 0887-6258
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1988.140260704
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular theory of transport in fluid microstructures: Diffusion in interfaces and thin films (1985)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1178-1186 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gradient theory of equilibrium fluid microstructures is extended to nonequilibrium isothermal processes. The theory is applied to steady diffusion across liquid-liquid interfaces. It is shown that local equilibrium across a fluid-fluid interface is maintained even in the presence of very high diffusion fluxes and that the concept of an interface acting as an applied potential energy for a diffusing species is of limited utility. The theory is suited for practical, semiempirical calculations of structure, stress, and isothermal transport in systems containing interfaces.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690310716
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  • 4
    Electronic Resource
    Electronic Resource
    An analysis of caprolactam polymerization (1975)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 15 (1975), S. 386-393 
    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 versatile model for ε-caprolactam polymerization is presented. A deterministic, mathematical basis for obtaining the most probable distribution of molecular weights in batch polymerization is developed. Continuous polycaproamide production has been modeled and shown to give othe than most probable distribution in many cases. The effect of adding monofunctional agents has been investigated. Results of some preliminary studies toward determining the optimal reactor configuration are presented.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760150512
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  • 5
    Electronic Resource
    Electronic Resource
    Probe diffusion in polystyrene/toluene solutions (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 2629-2649 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The technique of forced Rayleigh scattering has been used to measure the tracer diffusion coefficient, Dt, for two photochromic dyes, azobenzene and Aberchrome 540, in polystyrene / toluene solutions, as a function of polymer concentration (79-90% by weight) and temperature (-15-+60°C). The dye diffusivity can be scaled quantitatively to the solvent diffusivity, permitting direct application of the Vrentas-Duda free volume predictions for binary systems. However, the scaling factors are not in agreement with the model assumptions. The temperature and concentration dependence of Dt above the solution glass transition temperature, Tgs, is in good agreement with the model, without any freely adjustable parameters. The value of Dt at Tgs is a very strong function of concentration, increasing by a factor of 103 as the polymer concentration is reduced from 90 to 80%; this is also in quantitative agreement with the model. It is demonstrated that the temperature dependence of Dt exhibits a distinct break in the vicinity of Tgs, with both the existence and the character of the break in qualitative agreement with the extension of the Vrentas-Duda approach to glassy solutions. However, a fundamental difficulty in the calculation of the polymer contribution to the solution free volume at temperatures well below the bulk polymer Tg is exposed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281311
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  • 6
    Electronic Resource
    Electronic Resource
    Experimental studies of phase separation in reaction injection-molded (RIM) polyurethanesPresented in part at the American Chemical Society 181st National Meeting Atlanta, 1981. To be published in the proceedings of the A.C.S. International Symposium on Fast Polymerization Reactions and Reaction Injection Molding, Plenum Publishing. (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 719-728 
    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 series of polyether polyol (polyoxypropylene capped with polyoxyethylene), 4-4′ diphenylmethane diisocyanate, and 1,4 butane diol urethanes were prepared by reaction injection molding with different levels of catalyst (dibutyl tin dilaurate). The degree of phase separation, morphology, and molecular weight were compared by dynamic mechanical spectroscopy, wide-angle x-ray scattering, optical microscopy, and gel permeation chromatography. Slowly reacted (uncatalyzed) samples displayed better phase separation, crystallinity, low molecular weight, and poor mechanical properties. Fast-polymerized (highly catalyzed) samples showed a high degree of phase intermixing, low crystallinity, high molecular weight, and good mechanical performance. Differences between these two behaviors are discussed with the aid of a simplified phase diagram. Slowly reacted samples phase-separate through nucleation and growth of large spherulites, while quickly reacted samples form a much finer, interconnected microstructure. Infrared studies of phase separation for slow systems are presented and used to discuss phase separation in fast polymerizations.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221111
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  • 7
    Electronic Resource
    Electronic Resource
    Friction coefficients in self-diffusion, velocity sedimentation, and mutual diffusion (1984)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 22 (1984), S. 909-910 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1984.180220513
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