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  • 1990-1994  (9)
  • 1950-1954
  • 1993  (6)
  • 1991  (3)
  • Polymer and Materials Science  (9)
  • 1
    Electronic Resource
    Electronic Resource
    Carboxylate-containing chain-extended polyurethanes (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 581-588 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyurethanes based on methylene bis(p-phenyl isocyanate), bis(hydroxymethyl) propanoic acid, and poly (tetramethylene oxide) were synthesized, and their morphology and physical properties investigated. The acid polyurethanes exhibited very poor phase separation and mechanical properties, but upon neutralization with alkali metals phase separation improved dramatically and the materials resembled tough elastomers. The choice of cation played a much less important role than hard segment content in determining morphology and properties. Small-angle x-ray scattering patterns of these ionic polyrethanes exhibit two peaks, one characteristic of scattering between the hard and soft domains and the other reflecting scattering from aggregates of ionic groups residing within the hard domains. While ionic aggregation is the primary driving force for phase separation in these materials, their morphology more closely resembles that for nonionic polyurethanes than that for conventional ionomers, because the ionic groups exist in blocks composed primarily of rigid diisocyanate residues.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290507
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamic rheo-optical characterization of a low-density polyethylene/perdeuterated high-density polyethylene blend by two-dimensional step-scan FTIR spectroscopy (1993)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 31 (1993), S. 1769-1777 
    Details
    ISSN: 0887-6266
    Keywords: FT-IR ; step-scan interferometry ; 2D-IR ; polyethylene ; rheo-optical characterization ; time-resolved vibrational spectroscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Dynamic mechanical analysis coupled with polarized step-scan FTIR transmission and two-dimensional correlation analysis (2D FTIR) has been used to monitor the submolecular orientational responses of the components of a semicrystalline 50 : 50 blend of low-density polyethylene (LDPE) and perdeuterated high-density polyethylene (d*-HDPE) to a small amplitude uniaxial 23.47 Hz sinusoidal mechanical strain. Perdeuteration of the HDPE component allowed the distinction of its response from that of the LDPE in the blend samples. The experiments were carried out at room temperature. Analysis of the data indicates that the crystalline parts of the two components reorient at different rates, with the functional groups of the high-density portion reorienting faster, in general, than those of the LDPE in response to the mechanical strain. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1993.090311210
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Viscosity, yield stress, slip, and natural convection of HSPAN gel-water dispersions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 48 (1993), S. 625-637 
    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: Three hydrolyzed-starch-polyacrylonitrile (HSPAN) copolymer materials tested as gel-water dispersions in a Brookfield rotating spindle viscometer exhibited velocity slip at solid boundaries and a yield stress. Dispersions with 0.5% HSPAN concentrations were about 20,000 times more viscous than water when the shear stress surpassed the yield stress and viscous power-law flow ensued. The apparent viscosity of an HSPAN gel-water dispersion was reduced by nearly an order of magnitude when tap water was substituted for deionized water. The apparent viscosity of the HSPAN gel-water dispersions decreased by about 30% after the fluid was continuously maintained at a temperature of 80°C for 1 week, and by an order of magnitude or more after 3 weeks under those conditions. In natural convection tests, the yield stress enabled an HSPAN gel-water dispersion to withstand greater temperature differences across a horizontal layer before inception of natural convection than a fluid without one. © 1993 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070480406
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  • 4
    Electronic Resource
    Electronic Resource
    Dielectric and morphological investigations of phase separation and cure in rubber-modified epoxy resins: Comparison between teta- and DDM-based systems (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 2037-2051 
    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: Real-time and equilibrium dielectric measurements, covering the frequency range 10-1-105 Hz, are reported on a series of rubber-modified epoxy resins, based on reaction of the diglycidyl ether of bisphenol A (DGEBA) with either triethylenetetramine (TETA) or diaminodiphenylmethylene (DDM). The rubber modifier used was a carboxyl-terminated butadiene acrylonitrile (CTBN) reactive oligomer and the phase-separated structure, the results of which was examined using both dielectric and electron microscopic techniques. The mixture was initially homogeneous, but after a short period of time, it underwent phase separation and this process was marked by the appearance of a dielectric peak associated with ion-charge migration within the occluded rubbery phase. Analysis of the peak provided information on the morphology of the system and these data were compared with information obtained from scanning electron microscopy. A phase-separated morphology was observed consisting of spherical rubber particles dispersed in an epoxy matrix. For high concentrations of rubber ≥ 10 wt %, precipitation of epoxy domains within the rubbery phase was observed. Detailed dielectric studies of the peak associated with phase separation revealed that in the case of the TETA system the peak continued to shift after vitrification, whereas in the case of DDM, it was invariant with time. The point at which the peak appears was used to determine the time at which phase separation occurred. Differences observed in the lower temperature dielectric spectra were associated with variations in the form of the phase structure and possibly reflect different degrees of densification of the matrix. Good agreement was observed between the predictions of the Maxwell - Wagner - Sillers (MWS) theory and experimental observation for these systems. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070471114
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  • 5
    Electronic Resource
    Electronic Resource
    A Monte-Carlo study of ring formation during step-growth polymerization in three dimensions (1993)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 2 (1993), S. 91-94 
    Details
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The formation of ring and chain molecules during an irreversible step-growth polymerization has been modelled on a three-dimensional twenty six choice cubic lattice, and examined by the Monte-Carlo method. Movements were not allowed in the system in this preliminary study. The limiting value of the extent of reaction was found to be p = 0,9837 (±0,0003), and the number fraction of molecules found to be rings was 0,300 (±0,045), but the weight fraction was much smaller, 0,056 (±0,005).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1993.040020107
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  • 6
    Electronic Resource
    Electronic Resource
    Interactions between polymeric containers and their contained solution: Modeling of polymer-water solute partitioning via coupled solvent-water partition coefficients (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 43 (1991), S. 1475-1482 
    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 interaction between several polymeric materials, typical of those that have application as parenteral product containers, and 16 marker solutes was evaluated. Polymers used included polypropylene, polyvinyl chloride, ethylenevinyl acetate, an olefin rubber, a polyester ether block copolymer, and various composites of these materials. In addition, the partitioning of solutes between two common PVC plasticizers (dioctyl phthalate and butyryl hexyl citrate) and water was also examined. Correlation between equilibrium interaction constants (Eb) (which describe the equilibrium distribution of a solute between contacting polymer and solution phases) and solute octanol-water (Po-w) or hexane-water (Ph-w) partition coefficients were in general poor for all materials studied. However, a bivariate linear interaction model relating Eb to both partition coefficients: \documentclass{article}\pagestyle{empty}\begin{document}$$ \log E_b = a\left( {\log P_{{\rm o} - {\rm w}} } \right) + b\left( {\log P_{{\rm h} - {\rm w}} } \right) + c$$\end{document} effectively mimicked the interaction behavior of all materials evaluated. The utilization of the developed models to facilitate container compatability assessments is discussed. In addition, the use of a critical ratio of binding constants for a pair of solutes is introduced as a means of qualitatively assessing the effectiveness of a particular solvent as a polymer model.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070430809
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  • 7
    Electronic Resource
    Electronic Resource
    Electrochemical and spectroelectrochemical study of copper bleomycin complexesCertain commercial products are identified to adequately specify the experimental procedure. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology. (1991)
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 519-526 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electrochemical behavior of the copper(II) complex of bleomycin, a glycopeptide antibiotic with antitumor activity, was investigated in several buffer systems using cyclic voltammetry, polarography, coulometry, and spectroelectrochemistry. The copper bleomycin complex exhibited irreversible one-electron reduction on glassy carbon and mercury electrodes and was electroinactive on platinum, gold, and silver. After the initial reduction process on mercury, the appearance of the Cu(0)/(II) redox couple indicated dissociation of the complex and subsequent reduction of the Cu(I) to the metal. In the presence of excess bleomycin, the Cu(II) reoxidized from the mercury electrode is rapidly complexed and no copper reduction process is observed. On glassy carbon, however, the Cu(I) bleomycin complex is stable and does not undergo further reduction, as demonstrated by spectroelectrochemistry at a reticulated vitreous carbon optically transparent electrode. Consequently, as with many metallo-organic redox processes, there appear to be several possible electrochemical pathways depending on the pH, the electrode materials, and the experimental time domain.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140030612
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of interfacial variables on metal-porcelain bonding (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 531-537 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: While ceramic-to-metal bonding has been used in many applications, the actual chemical and physical factors leading to optimum bond strength are not well understood. In this work, several variables affecting the bonding between dental porelain and a palladium alloy (85% Pd, 10% Cu, and 5% Ga) were investigated: (1) precoating the metal by sputtering various oxides before porcelaining; (2) preoxidation of the metal base before porcelaining; (3) porcelaining under reducing atmosphere; and (4) surface roughening at controlled levels before porcelaining.Using a modification of the push doughnut shear bond strength test to measure bond strength the following results were obtained. (1) Compared with standard “control” samples, the aluminum oxide precoated precoated specimens showed a bond strength improvement of 46%, while the copper, manganese, and tin oxide precoatings exhibited smaller effects. (2) Preoxidation of the metal base led to pronounced bond strengthening (152%) by surface roughening as well as oxide formation. (3) Porcelaining under a reducing atmosphere severely reduced bond strength (88% lower than the controls) indicating the role of oxidation during the standard firing cycle. (4) Mechanical roughening of the surface by controlled amounts gave pronounced improvements with greater notch depth. Coarse roughening produced the highest bond strength improvements (486%). © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820270414
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  • 9
    Electronic Resource
    Electronic Resource
    Quantitative thin-film analysis with an energy-dispersive x-ray detector (1993)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 20 (1993), S. 111-114 
    Details
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Recent mathematical approximations of φ(ρz), the depth distribution of electron-excited x-rays, have opened up the possibility of accurate quantitative analysis of thin-film specimens by electron beam techniques. This method has been used extensively in electron probe microanalysis. This paper demonstrates quantitative analyses of thin films using energy-dispersive x-ray analysis (EDS) coupled with the φ(ρz) method. Metal and oxide films were analyzed by several techniques, including electron probe microanalysis (EPMA), Rutherford backscattering spectroscopy (RBS), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), spectroscopic ellipsometry (SE) and x-ray fluorescence spectroscopy (XRF); the results were compared with those obtained from the EDS thin-film analysis. In the case of Al2O3 films, EDS film thickness results agree to within ±4%, ±7% and ±9% of the TEM, EPMA and SE results, respectively. For metal films, the EDS results agree to within ±12% (thicknesses) and ±7% (composition) of the RBS, EPMA and XRF results.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/sia.740200204
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