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  • Polymer and Materials Science  (46)
  • 2005-2009
  • 1990-1994  (32)
  • 1980-1984  (14)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    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: This work reports on the photodegradation of low-density polyethylene films formulated with titanium (IV) oxide actylacetonate (TAc) and titanium dioxide pigment in different proportions; no previous reports on the photoactivity of this acetylacotonate have been found. Samples of blow-extruded films were submitted to accelerated UV aging with fluorescent lamps and the polymer degradation measured. The changes in carbonyl groups, molecular weight, and film elongation at break are discussed. The results show that TAc can promote photooxidation and accelerate the film degradation. The retention percent of elongation at break (EB) is apparently proportional to the carbonyl index irrespective of the formulation but has different relations with molecular weight (Mn), time, or the number of chain scissions (n), probably as a result of microstructural differences. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1579-1592 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential scanning calorimetry (DSC) has been utilized in several studies on polymerization kinetics, at different heating rates. However, there are several factors affecting the precision of kinetic parameters. In this work, the activation energy of urethane-bond formation between 2,6-tolylene diisocyanate and diethylene glycol is reported, the latter being in excess in order to minimize problems such as thermal transitions and incomplete reaction in the final step. The DSC technique was applied at different heating rates. Both the equal conversion and equal conversion rate options of the method are discussed. The latter appears to be a more adequate option for the system studied here. The results obtained show a good agreement with the model used.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1539-1542 
    ISSN: 0887-624X
    Keywords: polymerization ; ethylene ; polyethylene ; catalyst ; zeolites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ethylene polymerization has been studied in the presence of catalyst based on vanadium or vanadium-chromium supported on a zeolite HY. The effect of vanadium over chromium has been investigated as a function of the sequence of exchange of metals on the support and metal contents. Both effects were investigated in relation to the characteristics of the polyethylene (PE) obtained. Low activity has been found for the V (II) zeolite HY catalyst. Moreover, vanadium acts either as an inhibitor or as a promoter for the polymerizing activity of the Cr (III)/zeolite catalyst, depending on the preparation method. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 2 (1993), S. 133-141 
    ISSN: 1057-9257
    Keywords: CdS ; Chemical deposition ; Photodetector ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Very interesting behaviour is shown by chemically deposited CdS thin films for optoelectronic applications after air and vacuum (10-5 Torr) annealing. Vacuum annealing of samples at about 100°C caused the dark conductivity to improve by five orders of magnitude. The dark and photoconductivity of air-annealed (at around 200°C) samples increased by seven and two orders of magnitude respectively. Air-annealed (at 350°C for about 2 min) samples exhibited a very quick photoresponse (〈2 s for two decades of photocurrent decay) with σp/σd ≈ 105 for a bias of 10 V, which may be exploited for photodetector applications. Air or vacuum annealing of samples for a minimum of 10-15 min caused the optical transmittance above the band edge to increase by 10%-15% and annealing the sample at 200°C caused the absorption edge to shift towards the longer-wavelength region compared with the as-prepared and 100 and 350°C annealed films.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 1 (1992), S. 117-121 
    ISSN: 1057-9257
    Keywords: Tin(II) sulphide ; Tin(IV) oxide ; Photoconductor ; Air annealing ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: The thermal decomposition of chemically deposited SnS thin films to SnO2 films by air annealing at temperatures up to 400°C is discussed. The conversion of a 0.7 μm thick SnS thin film to an SnO2 film involves the creation of non-stoichiometric SnS, SnS + SnS2 mixed phase and non-stoichiometric SnO2 (i.e. SnO2 — x), as concluded from X-ray diffraction patterns, optical transmission spectra and electrical characteristics. The SnO2 thin films obtained in this manner are photoconductive, with a lowest sheet resistance (in the dark) of about 105 Ω/□ and an activation energy (Ea) of 0.1 eV for the electrical conductivity observed for the SnS films annealed at 325°C. This was found as the onset temperature for conversion of the SnS + SnS2 phase to the non-stoichiometric SnO2 - x film. Elevation of the annealing temperature to 400°C results in an elevation of the sheet resistance to about 109 Ω/□ with the value of Ea at 1.3 eV, indicating an improvement in the degree of stoichiometry.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 4 (1993), S. 99-105 
    ISSN: 1042-7147
    Keywords: Proton-conducting polymer ; Sol-gel process ; Battery ; Supercapacitor ; 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
    Notes: A new proton-conducting polymer electrolyte - poly-(benzylsulfonic acid)siloxane (PBSS) - has been prepared by sol-gel process. Both the hydrolysis and the condensation reactions of triethoxybenzylsilane have been studied under different catalysis conditions. The basic material - polybenzylsiloxane (PBS) - is always soluble, no matter what the experimental conditions, reaching an average molecular weight - Mw - of 20,000 and a polydispersity index close to 5. Good yields of a water-soluble polyelectrolyte - PBSS-thermally stable up to 300°C in air according to thermogravimetric analysis (TGA), and for which the exchange capacity is close to 4.4, can be obtained by sulfonation of PBS. Conductivities ranging from 2 × 10-3 to 10-2 S/cm at room temperature have been determined by a.c. impedance spectroscopy. These high conductivities, as well as the tensile strength of the PBSS, allow its use in several electrochemical devices.
    Additional Material: 8 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 2 (1993), S. 99-103 
    ISSN: 1057-9257
    Keywords: Buffer layers ; Laser ablation ; Superconducting films ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Ceramic thin films of yttria-stabilised zirconia (YSZ), SrTiO3(STO) and CeO2 have been deposited on Si(100) substrates by laser ablation. The films have been characterized by X-ray diffractometry, field emission scanning electron microscopy and secondary ion mass spectrometry (SIMS). The effects of the oxygen partial pressure during deposition and the substrate temperature were studied. All the films have preferential orientation: (h00) and (hh0) for STO and (hhh) for CeO2 and YSZ. The films show a low density of particulates and a very smooth surface. SIMS profiles indicate a low interdiffusion between film and silicon. One of the applications of these materials is their use as a buffer layer for the growth of YBCO on silicon. Because both materials are highly reactive, it is necessary to put a barrier between YBCO and silicon. For this purpose we used the ceramic films previously deposited in order to obtain superconducting YBCO films. The deposited YBCO films present good superconducting properties with zero resistance at temperatures between 80 and 85 K.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 46 (1992), S. 571-580 
    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 kinetic parameters for the polymerization reactions of two polyurethane systems were determined by using an improved method of differential scanning calorymetry (DSC). The calculated activation energy, reaction order, and Arrhenius prefactor show good correlation with the experimental results. The method used here shows several improvements as respects to other DSC methods: the three kinetic parameters can be calculated directly; it is more accurate than other DSC methods; and it requires only one heating rate, during the calorimetric experiments, to determine the activation energy.
    Additional Material: 12 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 1565-1573 
    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 thermal degradation of a poly(vinyl chloride) (PVC) resin was studied using a non-isothermal thermogravimetric technique. Kinetic parameters such as activation energies, reaction orders, and preexponential factors are calculated using integral and differential methods reported in the literature. Advantages and disadvantages of these methods are discussed in order to characterize PVC. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 27 (1982), S. 4467-4470 
    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: Dilute solution behavior of a cationic polyelectrolyte was studied with respect to acetic acid concentration using chitosan. The reduced viscosity, ηsp/C, of chitsan solutions increases with a decrease in the polymer concentration. For a given polyelectrolyte concentration, the specific viscosity is higher at lower acid (acetic) concentration, indicating the expansion of the polyelectrolyte chain due to electrostatic repulsion as a result of the interactions between chitosan and the solvent. The relationship between intrinsic viscosity [η]∞ and acetic acid concentration suggests no conformational transition of the chitosan molecules and possible formation of intramolecular hydrogen bonds during the shrinking of the hydrodynamic domain of the polyions.
    Additional Material: 4 Ill.
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