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  • Chemistry  (20)
  • SPACE RADIATION  (4)
  • Computer Systems
  • 1990-1994  (23)
  • 1935-1939  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Phenomenological model for the unified studies of different physical properties of polymers (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 207 (1993), S. 9-21 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird ein phänomenologisches Modell vorgestellt, mit dem sich das Entstehen starker Anisotropien der physikalischen Eigenschaften semikristalliner Polymerer nach einachsigem Verstrecken beschreiben 1äßt. Dieses Modell führt die Temperatur als expliziten Parameter in die Orientierungsfunktion ein. Es enthält zwei frei wählbare Parameter, die für jedes Polymere durch Anpassen der experimentellen Daten der Doppelbrechung als Funktion des Verstreckverhältnisses bei einer bestimmten Temperatur ermittelt werden konnen. Die berechneten Werte für Elastizitätsmodul, thermische Leitfähigkeit und Expansibilität parallel und senkrecht zur Streckrichtung stimmen in einem wäiten Bereich des Verstreckverhältnisses und der Temperatur mit den experimentellen Ergebnissen gut überein.
    Notes: A phenomenological model has been proposed to understand the development of strong anisotropy in physical properties of semicrystalline polymers on uniaxial drawing. The proposed model introduces temperature as an explicit parameter in the orientation function. The model contains two free parameters for each polymer which can be evaluated by fitting the experimental data on birefringence versus draw ratio at a particular temperature. The calculated values of elastic moduli, thermal conductivity and expansibility along and perpendicular to the drawing direction over the entire range of draw ratio and a wide range of temperature are in good agreement with experimental values.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052070102
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and evaluation of a polyimide containing carbazole and naphthalene moiety (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3795-3800 
    Details
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080281322
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  • 3
    Electronic Resource
    Electronic Resource
    Production, purification, and characterization of xylanase from a hyperxylanolytic mutant of Aspergillus ochraceus (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 244-251 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Enhancement of the productivity of xylanase and β-xy-losidase of Aspergillus ochraceus was investigated by multistep mutagenesis. The spores of the wild strain were subjected to UV and N-methyl-N-nitro-N-nitro-soguanidine (NTG). The hyperxylanolytic mutant (NG-13), which showed good clearing on the surface of the xylan-agar plate, secretes xylanase and β-xylosidase at high levels during growth on commercial xylan and on agricultural wastes. Both liquid and solid state cultures were employed in the study for enzyme production. The xylanase from NG-13 was purified to homogeneity by ammonium sulfate precipitation and gel filtration. This purified enzyme showed a pH optimum of 6.0 and was stable in the range of pH 5 to 10. Prolonged stability of the enzyme was observed at 45°C though its activity was maximal at 50°C. The molecular weight of the enzyme was estimated to be 4.3 × 104 by SDS-polyacrylamide gel electrophoresis and 5 × 104 by gel filtration on Sephadex G-75. The kinetic data showed that the Km and Vmax values for xylan were 1 × 10-3M and 19.6 μmol/ min/mg protein, respectively. The enzyme was both more active and thermostable in the presence of K+and was inactivated by thiol reagents such as Hg2+, p-hydroxymercuribenzoate (PHMB), 3′, 5′-dithiobis (2′-nitrobenzoic acid) (DTNB), and N-ethylmaleimide (NEM).
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260350305
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  • 4
    Electronic Resource
    Electronic Resource
    Crystallization study of a thermoplastic polyimide (new-TPI) (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 737-747 
    Details
    ISSN: 0887-6266
    Keywords: Crystallization ; melting ; morphology ; thermoplastic polyimide ; New-TPI ; PMDA ; 33BAPB ; polarizability ; SAXS ; lamellar thickness ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Crystallization, melting, and morphology of a thermoplastic polyimide (New-TPI) containing pyromellitic dianhydride (PMDA) and 3,3'-bis(4-aminophenoxy) biphenyl diamine (33BAPB) moieties have been studied. This material showed a glass transition temperature (Tg) of 250°C, an equilibrium melting temperature (T°m) of 406°C and a heat of fusion (ΔH) for 100% crystallinity of 6.38 kJ/mol. Measurements of the crystallization bulk rate (by DSC) and spherulite growth rate (by optical microscopy) indicated that the maximum crystallization temperature was about 320°C and the crystallization growth process was three-dimensional under thermal nucleation (the Avrami exponent n ca. 4). The rate of nucleation density was estimated to decrease with increasing temperature, and the product of two crystal surface free energies σeσo was calculated to be 1176 erg2/cm4. The meltgrown spherulite consistently showed a Maltese cross pattern with negative birefringence under cross-polars. The calculation of polarizability along the three unit cell axes suggested that the crystal b axis may be along the spherulite growth (radial) direction. Two scattering maxima were seen in small-angle x-ray scattering (SAXS) profiles. The dominant peak indicated a long period of ca. 20 nm which varied as a function of crystallization temperature. The weak peak at a d-spacing of 2.5 nm was independent of temperature and has been attributed to the chemical repeat distance determined by Okuyama et al. (indexed as 001). The lamellar thickness lc, estimated by the correlation function analysis of the SAXS data, was found to be similar to that determined by the Scherrer analysis of the 001 reflection peak. © 1994 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320415
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  • 5
    Electronic Resource
    Electronic Resource
    On the nature of order in wholly aromatic liquid crystalline random copolymers (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 30 (1992), S. 1375-1385 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystalline aromatic copolymers, solid state order in ; copolymers, wholly aromatic, nature of order in solid state of ; solid state order in aromatic liquid crystalline random copolymers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two different models of order in the solid state of wholly aromatic liquid crystalline copolymers (ALCPs), namely the nonperiodic layer (NPL) model of Windle et al. and the paracrystalline lattice (PCL) model of Biswas and Blackwell, have been analyzed with respect to experimental and theoretical observations. The NPL model proposes the formation of ordered domains by matching random sequences between adjacent chains while the PCL model relies on the presence of conformational correlations between adjacent monomers, without explicit sequence matching, to form ordered domains. The presence of three-dimensional order in the quenched state of ALCPs has been reported previously. The initial stages of crystallization are very likely to be assisted by the presence of small sequence matched domains. However, the probabilities for the formation of NPL domains having sizes comparable to those observed experimentally in the quenched state are extremely small. The PCL model, on the other hand, is not hampered by probability statistics and also provides a better fit to the experimental wide-angle x-ray scattering data along the fiber (Z) axis. The reported calorimetric data on ALCPs are also inconsistent with the presence of significant motion between chains, which is required for the NPL crystal to grow during the process of annealing. In contrast, the observation of a slow crystallization process, which converts the quenched hexagonal phase to the ordered orthorhombic phase, is adequately described by the PCL model as occurring via local conformational changes and small axial shifts between adjacent monomers. The observations from dielectric relaxation, nuclear magnetic resonance and dynamical mechanical spectroscopy studies also favor the PCL model over the NPL model of order in the solid state of ALCPs. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1992.090301208
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  • 6
    Electronic Resource
    Electronic Resource
    Phosphoric acid cation exchange resins from chemically modified polyvinyl chloride (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 1703-1710 
    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: PVC modified by Cl displacement reaction with meta-aminophenol (MAP), bisphenol A (BISA), and phenolphthalein (PHEN) has been converted into phosphoric acid cation exchange resins. These resins have been characterized in regard to their structure, ion exchange properties, and thermal stability. The ion exchange capacities fall into the range 5.5-8.0 (meq/g) for the resins. The overall thermal stability is considerably higher than that for the corresponding sulfonic acid resins, as well as for the PVC-MAP, PVC-BIS A, and PVC-PHEN condensates. The resins exhibit ca. 4-6% capacity losses under isothermal hydrolytic cleavage at 100°C for 24 h.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400924
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis and thermal stability, dielectric, and conductivity characteristics of some carbazole-bearing pendant and backbone sulfones (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1685-1692 
    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: A group of poly(N-vinylcarbazole) pendant polysulfones has been prepared by reacting it with benzene, toluene, p-chlorobenzene- and p-nitrobenzenesulfonyl chloride and N-methyl carbazole, 3,6-disulfonyl chloride by the Friedel Crafts reaction. Carbazole-based backbone polysulfones have also been prepared by the reaction of N-methyl carbazole, 3,6-disulfonyl chloride and biphenyl, naphthalene, anthracene, and carbazole in presence of anhydrous aluminum chloride. The various sulfone polymers, thus prepared, have been structurally characterized by elemental analysis and IR spectroscopy. Detailed analyses of thermal stability, dielectric, and conductivity characteristics have revealed certain significant differences between these two types of sulfone polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451001
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal, stability, morphological, and conductivity characteristics of polypyrrole prepared in aqueous medium (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 51 (1994), S. 1575-1580 
    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 aqueous polymerization of pyrrole with varying FeCl3/Py mol ratio produces black insoluble powders. IR characterization reveals the shifting of the N—H stretching band to higher frequency with increasing FeCl3 amount in the feed composition due to lowering of intermolecular H-bonding. SEM shows a spongy texture of the polymer. TGA indicates the initial decomposition temperatures (180°-237°C) to be somewhat dependent on the FeCl3/Py feed ratio. DSC suggests the glass-transition temperature to be in the range 160-170°C for the polymers prepared with various feed compositions. The conductivity is also dependent on the FeCl3/Py feed composition and levels off at a value of ∼3 ohm-1cm-1. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070510907
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  • 9
    Electronic Resource
    Electronic Resource
    Polymer blend: A novel method for the preparation of a natural rubber-carboxylated nitrile rubber blend (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1007-1014 
    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: Bis(diisopropyl)thiophosphoryl disfulfide (DIPDIS) can be successfully used to form a blend comprising polar carboxylated nitrile rubber (XNBR) and nonpolar NR through a chemical link between the two. It is revealed from the study that the physical properties of the vulcanizates obtained from the NR-XNBR blend could be significantly improved by the judicious selection of the NR:XNBR ratio. These properties can further be improved by two-stage vulcanization as described in the procedure. The SEM study reveals that it is possible to form a coherent blend of NR and XNBR in the presence of DIPDIS. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520801
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  • 10
    Electronic Resource
    Electronic Resource
    Chemical modification of of polypyrrole. I. Preparation and structural characterization of polypyrrole electrophically substituted with phthalic anhydride and pyromellitic dianhydride (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 54 (1994), S. 843-847 
    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: Polypyrrole (PPY) prepared in ether and in aqueous medium has been modified by polycondensation with phthalic anhydride (PA) and pyromellitic dianhydride (PMDA) in presence of Friedel-Crafts catalysts such as anhydrous zinc chloride and anhydrous ferric chloride at high temperature. The substitution reaction between PPY and the anhydrides presumably proceeds by intra-and interchain resulting in the formation of intractable products. The characterstic carbonyl absorption band expected for C—O and diketone groups in the proposed structure for the polycondensates has been observed in spectra of the anhydride-modified poly-condensates. XRD pattern of the polycondensates is totally amorphous. © 1994 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070540702
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