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  • Polymer and Materials Science  (32)
  • 2000-2004
  • 1990-1994  (32)
  • 1
    Electronic Resource
    Electronic Resource
    Photodegradation of polyethylene films formulated with a titanium-based photosensitizer and titanium dioxide pigment (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 53 (1994), S. 847-856 
    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: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070530702
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  • 2
    Electronic Resource
    Electronic Resource
    Dextran functionalized by cyclic carbonate groups as supports of bioactive compounds (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 206 (1993), S. 77-85 
    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 werden Aspekte der Reaktion von Dextran mit Ethyl-chlorformiat und Triethylamin als Katalysator behandelt. Mittels 1H- und 13C NMR-Spektroskopie wurden in den gebildeten modifizierten Dextranen cyclische und acyclische Carbonatgruppen nachgewiesen. Vorversuche zeigten, daß die Reaktion cyclischer Carbonatgrupen mit verschiedenen Amin-Modellverbindungen stark vom Basencharakter des Amins abhängt. Phenethylamin und Tyramin wurden quantitativ an aktiviertes Dextran mit cyclischen Carbonatgruppen gebunden. Die Dextran-Phenethylamin- und Dextran-Tyramin-Addukte werden unter den angewendeten Bedingungen (pH 1,0 oder 9,1 bei 37°C) nicht heterogen hydrolysiert.
    Notes: This work deals with some features of the reaction of dextran with ethyl chloroformate using triethylamine as catalyst. The presence of cyclic and acyclic carbonate groups in the resulting modified dextrans was demonstrated by IR, 1H and 13C NMR spectroscopy. Preliminary experiments have shown that the reaction of cyclic carbonate groups with several model amines is greatly dependent on the basic character of the amine. Model amino type drugs (Phenethylamine and tyramine) were quantitatively bound to activated dextran with cyclic carbonate groups. The heterogeneous hydrolysis of dextran-phenethylamine or dextran-tyramine adducts showed that no hydrolysis takes place under the applied conditions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052060108
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis and controlled release behaviour of esters from amylose and 1-naphthylacetyl chloride (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 1513-1518 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the modification reaction of amylose with 1-naphthylacetyl chloride using pyridine as catalyst and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by IR, 1H and 13C NMR spectroscopy. A linear dependence of the reaction rate on the concentration of polymer, 1-naphthylacetyl chloride and pyridine was found. The activation energy was found to be 32,4 kJ/mol. The hydrolysis in the heterogeneous phase showed that the release of the active compound from tablets is dependent on the hydrophilic character of the modified amylose as well as on the pH value of the medium.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910704
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  • 4
    Electronic Resource
    Electronic Resource
    Some fundamental studies of the reaction of poly(vinyl alcohol) with alkyl chlorophosphates (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 1733-1739 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification reaction of poly(vinyl alcohol) with diethyl chlorophosphate and ethyl dichlorophosphate is studied in homogeneous phase using tertiary amines as catalysts. The structure of the modified polymers was determined by means of 1H and 31P{1H} nuclear magnetic resonance (NMR) spectroscopy as well as by chemical analysis. The structure of the polymers resulting from the reaction with diethyl chlorophosphate greatly depends on the reaction temperature as well as the catalyst. For lower reaction temperatures (≤25°C) only acyclic phosphate ester groups were observed. The activation energy was found to be 24,9 kJ/mol. The presence of cyclic phosphate ester groups was found, when higher reaction temperatures (〉25°C) were used. These results can be interpreted considering the existence of transesterification reactions. Crosslinking structures were obtained in case ethyl dichlorophosphate was used instead of diethyl chlorophosphate.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920807
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  • 5
    Electronic Resource
    Electronic Resource
    Activation energy for urethane-linkage formation. An improved calculation from the differential scanning calorimetry data (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 1579-1592 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1990.080280623
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  • 6
    Electronic Resource
    Electronic Resource
    Use of V and V-Cr catalysts interchanged in “Y” zeolites for the polymerization of ethylene (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 1539-1542 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080320814
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  • 7
    Electronic Resource
    Electronic Resource
    Solar cells with improved efficiency based on electrodeposited copper indium diselenide thin filmsThis work is supported by the Commission of the European Communities under a JOULE contract “Euro Cis” (JOUR-0045-C) and the CNRS-ADEME (contract No. 93N80/0016). Colleagues from the Institut für Physikalische Elektronik (Stuttgart) and the Royal Institute of Technology (Stockholm) are warmly acknowledged for stimulating exchanges in the frame of the EuroCIS group. (1994)
    Weinheim : Wiley-Blackwell
    Advanced Materials 6 (1994), S. 379-381 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19940060508
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  • 8
    Electronic Resource
    Electronic Resource
    Peroxidase-ferrocene modified carbon paste electrode as an amperometric sensor for the hydrogen peroxide assay (1991)
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 281-285 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new enzymatic amperometric sensor for hydrogen peroxide based on a modified carbon paste electrode is described. Horseradish peroxidase and ferrocene mediator were immobilized by dissolution or dispersion in a graphite-paraffin oil paste. To prevent losses of immobilized chemicals under operational conditions, the electrode surface was coated with a Nafion membrane. The device exhibits a relatively fast response time (42 s for 95% of the steady-state response) and yields currents linearly related to the hydrogen peroxide concentration over the 10-7 to 10-5 mol/L range in both static and flow injection operations. The slope of the calibration plot remained constant for more than 20 days. Flow injection assays of hydrogen peroxide at a sampling rate of about 70 injections per hour, with a relative standard deviation of 1.4%, are possible. An easy and low cost preparation procedure is described.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140030407
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  • 9
    Electronic Resource
    Electronic Resource
    Study of the radial and axial distribution of heavy metals in oak growth rings by stripping voltammetry (1991)
    Weinheim : Wiley-Blackwell
    Electroanalysis 3 (1991), S. 325-329 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concentrations of the heavy metals (Cd, Pb, Cu, and Zn) have been determined in oak growth rings from the polluted region of Königstein, Germany, by differential pulse anodic stripping voltammetry and compared to those in soil. The radial distribution was found to be the same for all four metals studied and features a distinct increase in the recent growth rings and a marginal increase in the transition zone between sapwood and heartwood. The toxic metals cadmium and lead are preferentially bound to lower parts of the tree, whereas for essential metals copper and zinc, monotonous axial distribution has been found in the range 0-5 m. This points to different degrees of mobility of heavy metal complexes in wood material.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140030413
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  • 10
    Electronic Resource
    Electronic Resource
    Determination of chromium(VI) and chromium(III) by using a diphenylcarbazide-modified carbon paste electrode (1993)
    Weinheim : Wiley-Blackwell
    Electroanalysis 5 (1993), S. 155-163 
    Details
    ISSN: 1040-0397
    Keywords: Chromium ; Modified Electrode ; Voltammetry ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A carbon paste electrode modified with diphenylcarbazide has been prepared in order to improve the analytical determination of chromium(VI) and chromium(III) using voltammetric techniques. Several parameters, such as carbon/diphenylcarbazide ratio, carbon/Nujol ratio, scan rate, accumulation time, etc., have been explored. A voltammetric study of both chemical species and an explanation of the chemical and electrochemical mechanism are presented. When applied to assays of soil samples, the results compared favorably to those of a polarographic method.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140050211
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