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  • 1990-1994  (5)
  • 1975-1979
  • 1965-1969  (2)
  • 1940-1944
  • Chemistry  (7)
  • 1
    Electronic Resource
    Electronic Resource
    A simple model of nonisothermal coextrusion (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 408-415 
    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 numerical method has been developed that takes the streamline finite difference method for modeling fully developed multilayer polymer flows and adds to it a simple means of accounting for nonisothermal conditions. In industrial practice, temperature control is often used to match material viscosities and, thereby, to avoid flow instabilities. By numerically calculating both viscosity ratios and normal stress difference ratios, the numerical method allows one to judge the relative stability of different flows and to choose an intelligent set of experiments when designing a coextrusion process. The algorithm has been successfully tested for a number of polymer melt constitutive equations in flows where the viscosity jumps no more than two orders of magnitude between fluids. Results for a rheologically well characterized polystyrene low-density polyethylene system and for an industrially interesting high-density polyethylene/Ultem system show that the common practice of matching zero-shear viscosities is overly simplistic when interface shear rate, conduction, normal stress, and flow rate effects are taken into account.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760300705
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  • 2
    Electronic Resource
    Electronic Resource
    Metallocene catalysts for olefin polymerizations. XXIV. Stereoblock propylene polymerization catalyzed by rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl)(1-η5-indenyl)dimethyltitanium: A two-state propagationSee Reference 1. (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2601-2617 
    Details
    ISSN: 0887-624X
    Keywords: Ziegler-Natta catalysts ; ansa-metallocene catalyst ; thermoplastic elastomeric poly(propylene) ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Racemic-anti-[ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dimethyltitanium (6) has been synthesized and its molecular structure determined by x-ray diffraction methods. The two Ti=Me(1) and Ti=Me(2) units have bond distances differing by 0.08 Å and their proton NMR resonances are separated by over 1 ppm. Using this compound and methylaluminoxane (MAO) as the activator, at 25°C the 6/MAO catalyst produced polypropylene having crystalline domain with physical crosslinks. The polymers obtained at lower polymerization temperatures are rheologically liquids. The behaviors of this catalyst system resembles closely the previously reported rac-[anti-ethylidene(1-η5-tetramethylcyclopentadienyl) (1-η5-indenyl)dichlorotitanium (4)/MAO system. The structure of 6 determined here furnishes tangible support for the proposed two-state (isomeric)-switching propagation mechanism. Addition of MAO to 6 causes broadening of the Me(1) resonance in the 1H-NMR spectra, and 6 is decomposed by Ph3C+B(C6F5)-4. © 1992 John Wiley & Sons, Inc.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301215
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  • 3
    Electronic Resource
    Electronic Resource
    Rheology of phase separated blends of two thermotropic liquid crystalline copolyestersPresented at “Liquid Crystal Polymer Symposium,” Amherst, Mass., July 1990. (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 773-776 
    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 melt rheology of phase separated blends of two thermotropic liquid crystalline polymers (LCPs) have been studied. The two components are a random copolyesters consisting of 73 mol% 4-hydrobenzoic acid (HBA) and 27 mol% 6-hydroxy-2-napthoic acid (Vectra A900 of Hoechst Celanese Corp.) and a poly(ethylene terephalate-co-4-oxybenzoate) containing 60 mol% HBA units (PET/60HBA of Eastman Kodak Corp.). Most striking is the effect of adding 10% PET/60HBA to Vectra A900: The viscosity at 290°C drops by a factor of 4 and the terminal zone of the relaxation time spectrum is shifted to much shorter times. This is an interesting effect that could be used for LCP processing even if its origin is not yet understood. Differential scanning calorimetry measurements support the hypothesis that the blend is phase separated and that no transestification reaction occurs during the experiments.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321203
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  • 4
    Electronic Resource
    Electronic Resource
    Optical anisotropy of a thermotropic liquid-crystalline polymer in transient shear (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1571-1588 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A rheo-optical apparatus, based on a linear shear rheometer, has been constructed to study the deformation of liquid-crystalline polymers. This apparatus uses optical techniques such as flow birefringence, small-angle light scattering, and optical microscopic image analysis. The rheological responses were simultaneously measured under varying temperatures and deformation conditions. The modified Debye-Bueche equation for scattering, in the nonspherically symmetrical form, was adapted to analyze small-angle light-scattering data. The orientation correlation lengths, determined by this method, reveal the deformation mechanism in nematic melts. Flow birefringence results are in agreement with the proposed mechanism.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280912
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and properties of an easy-processable bismaleimide thermoset resin (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 451-459 
    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: Reaction of methylenedianiline and maleic anhydride in acetone, followed by cyclodehydration in the presence of acetic anhydride and 1,4-diazabicyclo [2.2.2] octane as a catalyst, affords a mixture of compounds, Desbimid, with maleimide, isomaleimide, and acetamide groups. Dissolution of this mixture in styrene and 2-hydroxyethyl methacrylate results in clear liquid resins. The viscosity of the formulated resins ranges from 100-1700 mPas at 25°C depending on the concentration of Desbimid. These systems can be processed and cured at ambient temperatures until demoulding and postcured at temperatures up to 200 or 250°C. The flexural modulus, flexural strength, and elongation at break of a number of cured formulations are found between 3500-3800 N/mm2, 90-115 N/mm2, and 2.7-3.5%, respectively.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450310
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  • 6
    Electronic Resource
    Electronic Resource
    Über den Mechanismus der Reaktion zwischen Alkansulfonylchloriden und Phenolaten (1969)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 311 (1969), S. 596-603 
    Details
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bei der Umsetzung von Isopropyl-, Neopentyl- und Cyclohexylsulfochlorid mit Natriumphenolaten in Gegenwart von D2O entstehen α-monodeuterierte Alkansulfonsäurearyl-ester. Bei der Umsetzung von 2-Deutero-2-propylsulfochlorid mit Natriumphenolat tritt ein kinetischer Isotopieeffekt kH:kD∼4,5 auf. Offenbar verlaufen die untersuchten Reaktionen nach einem Eliminierungs-Additions-Mechanismus über Sulfene als Zwischenprodukte.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19693110409
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  • 7
    Electronic Resource
    Electronic Resource
    Die stereoregulierte homo- und copolymerisation des butadiens (1967)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 101 (1967), S. 320-336 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The preparation of homopolymers of butadiene in the presence of cobalt and vanadium-containing ZIEGLER-catalysts is reported and the influence of water on the reaction system is investigated. Furthermore, the preparation of copolymers of butadiene with isoprene, 1,3-pentadiene, and styrene in the presence of the catalysts is described and the technical properties of the polymers discussed.While, the homopolymers have a sterically uniform structure, butadiene is sterically less regularly introduced into the copolymers. Only in the case of containing catalysts, butadiene is homo- and co-polymerized in 1,4-trans position.Individual technical properties of the copolymers yet not the properties as a whole are superior to 1,4cis-polybutadiene.
    Notes: Es wird über die Darstellung von Homopolymeren des Butadiens mit Hilfe von kobalt und vanadinhaltigen ZIEGLER-Katalysatoren berichtet und der Einfluß des Wassers im Reaktionssystem untersucht. Ferner werden die Herstellung von Copolymeren des Butadiens mit Isopren, Pentadien- (1,3) und Styrol mit diesen Katalysatoren geschildert und die anwendungstechnischen Eigenschaften der Polymeren besprochen.Während die Homopolymeren einen sterisch weitgehend regelmäßigen Aufbau besitzen, wird das Butadien in den Copolymeren in fast allen Fällen weniger regelmäßig eingebaut. Nur mit vanadinhaltigen Katalysatoren wird Butadien auch in den Copolymeren ausschließ-lich in 1,4-trans-Stellung incorporiert.Die Copolymeren übertreffen zwar in einzelnen anwendungstechnischen Eigenschaften das 1,4-cis-Polybutadien, nicht jedoch in den Gesamteigenschaften.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1967.021010118
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