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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1693-1700 
    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: Textures of the ethyl cellulose (EC)-dichloroacetic acid (DCA) mesomorphic solution were studied systematically by polarizing microscopy and small-angle light scattering. It was found that with increasing polymer concentration, the mesophase could show a disklike texture, an oil streak texture, a pseudoisotropic texture, and an iridescent planar texture. Within the mesophase the ordering degree is different in different zones. The phase transition between anisotropic and isotropic phases could also be accomplished by changing temperature. With increasing temperature the mesophase with the lower degree of order could first transform to the isotropic phase and the phase transition from an anisotropic phase with a higher degree of order to the isotropic one could take place only at the higher temperature. A disklike texture was also observed during the phase transition between the anisotropic and isotropic phases when the solution was heated and it was probably a basic texture in polymer cholesteric liquid crystals.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 39 (1990), S. 2353-2375 
    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: Open-loop optimal temperature control strategies for the batch free radical polymerizations of styrene are investigated using the minimum principle. Two kinetic models, one considering the gel effect and the other incorporating both the gel effect and the glass effect, are employed. By using the Min-H strategy, a control variable program that minimizes one objective function and yields values of other terminal quantities can be obtained. It is found that the optimal temperature programs are highly dependent upon the kinetic characteristics of reactions. The gel and glass effects, which control ultimate molecular weights, play important roles in affecting the temperature programs. Numerical examples using two objective functions, one in which reaction time is minimized, and the other in which molecular weight distribution is minimized, are presented. The theoretical predictions using kinetic model with the gel and glass effects are also compared with experimental measurements of conversion, molecular weight, and molecular weight distribution. Although the agreement between the experimental work and the theory is less than satisfactory, the trends of policy improvements are consistent.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1979-1984 
    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: Thermotropic behavior of hydroxyethyl celloulose acetate (HECA) was studied by polarizing microscopy, DSC, and X-ray diffraction. It was found that HECA was an anisotropic liquid between the temperature from 130 to 185°C on heating, and when the temperature was over 185°C, it became isotropic. In cooling, however, mesophase began to form at about 165°C. The transformation temperature decreased with decreasing molecular weight and the temperature region of transformation decreased with decreasing the distribution of the molecular weight for HECA. The kinetic ability of tranformation appeared the maximum with molecular weight. The HECA liquid crystal is cholesteric and the distance between layers of ordered molecular chains was enlarged when HECA was transformed from liquid crystalline glass to the liquid crystalline state. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 654-664 
    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: An experimental and theoretical study of reaction injection molding (RIM) of polyurea was conducted in this work. A lab-scale RIM machine was used to carry out the polyurea bulk polymerizations. A “free-table” viscometer was designed to measure the fast rheological changes and liquid-solid transition. A mathematical model was proposed to simulate the fast reaction and rheological changes in the polyurea RIM process. The parameters of this model were determined based on the solution polymerization data from FTIR and Haake rheometer measurements. Combined with an appropriate heat transfer equation, this model predicts fairly well the adiabatic temperature and viscosity rises of bulk polyurea reactions in RIM.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 125-132 
    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: Ethyl-cyanoethyl cellulose (E-CE)C/poly (acrylic acid) (PAA) composites were prepared by polymerizing acrylic acid (AA) in (E-CE) C/AA cholesteric liquid crystalline solutions. The morphology and structure and the compatibility of composites prepared in different conditions were studied by small-angle light scattering (SALS), differential scanning calorimetry (DSC), X-ray spectrometry, polarizing microscopy, and electron microscopy. Ho-mogeneous composites with the cholesteric structure could be obtained by photopolymerization. During the photopolymerization, however, the morphology of the liquid crystalline domains became crylindric and the axial direction of the cylindric domain was at an angle of about 45° to the layers of the ordered molecular chains. The polymerization initiated by azobisisobutyronitrile (AIBN) resulted in the phase separation. The morphology of the liquid crystalline domains was maintained although the cholesteric structure of the composite was partly destroyed. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 533-540 
    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: Ethyl-cyanoethyl cellulose [(E-CE)C]/cross-linked polystyrene (PS) composites were prepared via polymerization of styrene in (E-CE)C/styrene solution with glycol diacrylate as a cross-linking reagent. The polymerization of the solution, morphology, and miscibility of (E-CE)C/PS composites were studied with polarizing microscopy, small-angle light scattering (SALS), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). It was found that the mixing state of the (E-CE)C/PS system and the thermal stability of composites were modified by cross-linking of PS. In the intensively cross-linked composite prepared from the anisotropic solution, there existed cylindrical domains in which (E-CE)C spherulites were dispersed in PS. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 684-692 
    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 free radical copolymerization model is proposed for simulating the reaction rates and conversions of styrene monomer and unsaturated polyester resins during curing. This model is based on film theory in which the rate constants reflect both reaction and diffusion resistances. Differential scanning calorimetry in combination with Fourier transform infrared spectroscopy is used to measure the overall and individual reactivities of reacting species. Model parameters are determined from experimental data. The applicability of this model is demonstrated in a cure simulation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 607-613 
    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 formation, textures, and optic characteristics of the ethyl-cyanoethyl cellulose [(E-CE)C]/acrylic acid (AA) mesophase were studied using polarizing microscopy, spectro-photometry, and small-angle light scattering (SALS). The disklike, oily streak, planar, pseudoisotropic, polygonal textures and the texture of domains gathered randomly were observed in the mesophase. The polygonal texture in unitary mesomorphic solutions can be regarded as the texture from the combination of deformed mesophase aggregates with the disclike texture. The mesomorphic solution exhibits vivid colors when the concentration is about 42-52 wt % because of its selective reflection to visible light. The wavelength of the light that is selectively reflected shifts to the shorter wavelength, with increasing concentration. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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