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  • Chemistry  (6)
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  • 1
    Electronic Resource
    Electronic Resource
    Effect of molecular structure on rheological and crystallization properties of polyethylenes (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2317-2333 
    Details
    ISSN: 0887-6266
    Keywords: isothermal crystallization ; quiescent ; oscillatory shear ; molecular structure ; HDPE ; long-chain branching ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This article describes the development of reliable techniques to measure the isothermal crystallization rates (ICR) under quiescent as well as under small amplitude, oscillatory shear conditions. Quiescent crystallization rates were obtained using a differential scanning calorimeter. Those under small amplitude shear were obtained using Rheometrics rheometers. It is shown how a small amount of long-chain branching in high-density polyethylene homopolymer (HDPE) dramatically influences rheological properties and enhances ICR. For these HDPEs, the rate increases with the increase in long-chain branching. The general application of isothermal crystallization studies, however, should be done with great caution. This is because the fundamentals of isothermal crystallization require that it be done on the basis of a fixed undercooling with respect to the equilibrium melting temperature. Such a temperature is ill-defined for the commercial polymers having broad molecular weight distribution (MWD). Nonetheless, a practical procedure is outlined wherein the melting curve of a previously isothermally crystallized sample is used as a substitute for judging the equilibrium melting point and in deciding the selection of a proper crystallization temperature. Even this new procedure may not be applicable for polymers having heterogeneous short-chain branching distribution. © 1996 John Wiley & Sons, Inc.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Polybutadiene content and microstructure in high impact polystyrene (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 59 (1996), S. 953-959 
    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 polybutadiene (PB) content and its microstructure in different grades of high impact polystyrene (HIPS) has been studied by various spectroscopic techniques. PB is characterized by deformation bands in FTIR spectroscopy at 994, 967, 912, and 729 cm-1. FT-Raman was used for higher constant resolution over the range of wave numbers. It provides reasonable signal to noise ratios in near IR excited Raman. Proton and 13C-NMR spectroscopy was utilized for the determination of polybutadiene content in HIPS and tacticity, and reactivity ratios. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Supermolecular morphology of thermoreversible gels formed from homogeneous and heterogeneous solutions (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1819-1835 
    Details
    ISSN: 0887-6266
    Keywords: polystyrene ; polyethylene ; gelation mechanisms ; morphology ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The supermolecular structures of thermoreversible gels formed from either homogeneous or heterogeneous solutions were examined by scanning electron microscopy. The morphologies of gels of polyethylene and polystyrene of various tacticities were then related to the phase diagram of the polymer-solvent system. We confirmed the morphological findings of Aubert on isotactic polystyrene gels formed either above the binodal or inside the spinodal and extended his study to gels prepared within the metastable region of the phase diagram. For polystyrenes and polyethylene, the morphology of the gels formed inside the coexistence curve differs markedly from that of gels formed outside. Inside the binodal, gels of polyethylene and polystyrenes exhibit remarkable morphological similarities, indicating a common gelation mechanism, namely, liquid-liquid phase separation. Depending on the concentration, these gels exhibit either an open strut-like network structure or smooth spherical globules. The former is attributed to gelation inside the spinodal whereas the latter is believed to result from gelation in the metastable region. For crystalline polymers, gels formed inside the coexistence curve subsequently undergo crystallization within their polymer-rich phase. The morphology of isotactic polystyrene and polyethylene gels formed outside the binodal consists of overlapping lamellar structures, whereas that of atactic and epimerized polystyrene gels is characterized by a sheet-like structure, differentiating the crystallization-based mechanism from others. © 1993 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311215
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  • 4
    Electronic Resource
    Electronic Resource
    Chain-scission and yellowing in high impact polystyreneNCL communication No. 5996. (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 36 (1995), S. 309-313 
    Details
    ISSN: 0959-8103
    Keywords: high impact polystyrene ; polychromatic irradiation ; viscosity ; tensile impact ; yellowing ; 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: Different grades of impact-modified polystyrene were studied by viscometry, tensile impact test and colour change upon exposure to polychromatic irradiation at 55°C in air. The samples underwent extensive reduction in intrinsic viscosity [η] and tensile impact strength, and yellowed upon polychromatic irradiation (λ ≥ 290 nm). Chain-scission during photo-oxidative degradation was also studied under conditions where evolution of volatiles was negligible. Tristimulus values were calculated for unirradiated and irradiated samples. The rate of oxidative degradation was maximum in the sample possessing higher unsaturation content.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210360402
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  • 5
    Electronic Resource
    Electronic Resource
    In vitro corrosion and tarnish characterization of typical dental gold compositionsThis paper was presented at the eleventh International Biomaterials Symposium in conjunction with the Fifth Annual Meeting of the Society for Biomaterials at Clemson, SC, April 1979. (1981)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 15 (1981), S. 191-201 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Analysis of the anodic polarization and alternate immersion test response of 16 precious metal alloys with compositions similar to those of commercial dental golds indicate that alloys containing high (Ag + Cu) contents are likely to be more corrosion and tarnish prone. It also appears that the alloys containing high precious metals contents (Au, Pt, and Pd) are characterized by immunity or anodic film protection over a range of anodic overpotentials, indicating superior corrosion resistance.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820150207
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of thermal annealing on alpha irradiated cellulose nitrate electrets (1985)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 36 (1985), S. 341-342 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1985.010360610
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