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  • 1
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of Melanin-concentrating hormone (MCH) fragments have been synthesized and their biological activities compared with the parent peptide. The substructural units, 5-14 linear and 5-14 cyclic, have been used as models for MCH -  in 1H-nmr conformational studies. Conformational features predicted by molecular dynamics analyses find support in the nmr experiments.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 19 (1975), S. 461-480 
    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: Acrylic acid (AA) and acrylonitrile (AN) were used to carry out grafting on polyester (PE) fibers using the techniques of initiation by γ-radiation as well as benzoyl peroxide. The nature of the grafted fiber substance was found to be the same, irrespective of the grafting technique. Extent of grafting depended upon the time, concentration of the initiator, and the monomer as well as on the irradiation dose. The increase in the moisture regain was directly proportional to the amount of graft in the fiber. AA grafted fibers were rendered more hydrophilic than AN grafted fibers for equivalent amount of grafts. Considerable improvement in dyeability of the PE fibers was possible through grafting. About 50% to 100% improvement with disperse dyes was observed in case of PE fibers containing 22.4% and 9.0% graft of AA and AN, respectively. Intense fast dyeing with direct and basic (cationic) dyes was also possible, and the dye content was proportional to the extent of graft introduced in the fiber. The CN groups were reduced to NH2 groups in the AN graft on the fiber. In this way, deep, fast, and bright dyeing was obtained with reactive dyes. Electrokinetic studies were carried out on the grafted fibers. With the increased amount of AA graft, the maxima in the zeta potential curve shifted toward higher acidic pH as greater amounts of alkali was utilized by the —COOH groups in the graft. In this respect, CN groups were less sensitive due to their lesser polarity as compared to the carboxylic groups. It was observed from surface charge density (S.C.D.) studies that the effective surface area of the fiber decreased with the increase in the amount of graft, particularly in case of AN graft. Surface conductivity (S.C.) studies revealed that with increase in the number of polar groups (—COOH) on the surface of the fiber, the S.C. increased with the increase in the amount of AA graft. In case of AN grafts, the reduction in effective surface area of the fiber played a more important role than the contribution by the CN groups to surface conductivity.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 3
    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 technique of laser interferometry is now used routinely by the microelectronics industry for the measurement of the dissolution rates of thin polymer films. In addition to the rate of dissolution, laser interferometry can also provide quantitative information on the thickness of the transition layer between the dissolving glassy polymer and the liquid solvent. This paper describes how observed patterns of reflected light intensity may be analyzed to calculate the thickness of the transition layer for polymers that dissolve with little or no swelling. The technique requires knowledge of the shape of the concentration profile in the transition layer. However, by assuming various simple model profiles one may obtain a reasonable estimate. Experimental measurements of poly(methyl methacrylate) (PMMA) films dissolving in methylethyl ketone indicate transition layers of thicknesses 0 to 0.1 μm for PMMA of molecular weights Mw = 37,000 to 1,400,000.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 2695-2710 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new class of ethylene polymerization catalysts, namely the bis-(2,4-dimethyl pentadienyl) derivatives of titanium, vanadium, and chromium, have been synthesized and tested. When supported on a variety of inorganic carriers, these compounds yielded 0.2-1.0 million g polymer/g metal/h under typical slurry conditions. Sensitivity to H2 as a molecular weight regulator varied among the three metals, but in the absence of H2 all produced ultrahigh-molecular-weight polyethylene. The molecular weight distribution varied from moderately narrow to very broad (bimodal) depending on the metal and the carrier. Catalyst synthesis and polymer properties are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 29 (1991), S. 1301-1312 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cellulose-MMA graft copolymers have been produced using aqueous-based, Ce(IV)-initiated and periodate-initiated systems and also photochemical initiation. The reaction variables studied include the effect on grafting of varying the MMA monomer concentration, the initiator type and concentration, and also the reaction time. Of the three initiator types examined, the Ce (IV)-initiated and the photochemically-initiated systems are comparable in their effects on graft copolymer formation. Concurrent homopolymer formation was in the region of 50% by weight. Periodate-initiation leads to less efficient grafting of MMA onto cellulose, although homopolymer formation is also lower (typically 〈20% by weight). The characterization of the copolymeric products through their properties as solids and, as their carbanilated derivatives, through their solution properties has been undertaken. Values of the activation onergy of decomposition (EA) of the cellulose-MMA graft copolymers decrease with increasing MMA content, ranging between 227 and 155kJ mol-1. There is also a dependence on initiator type and grafting reaction conditions used (EA (cellulose wood pulp) = 239 kJ mol-1; EA (PMMA) = 115 kJ mol-1). Quantitative zeta-potential (ζ) determinations for cellulose-MMA graft copolymer samples produce negative surface charge density (σ) values. At a comparable MMA grafting level of 70-80%, values are of the order: photochemical (-730 esu/cm2) 〉 periodate (-470 esu/cm2) 〉 Ce (IV)-initiation (-351 esu/cm2). Characterization of carbanilate solutions (by rheological examination) and of dry, carbanilate films (by study of surface wetting behavior) highlighted differences in the physical conformation of copolymers prepared by the different initiation routes. The highly degradative effect on cellulose of a periodate initiator, in comparison with the Ce (IV)-initiation system, is reflected in significantly reduced molar mass values (typically, Mn 65,000 as opposed to 130,000 for Ce (IV)-initiated graft copolymer carbanilates).
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 28 (1990), S. 3587-3601 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Another class of organochromium compounds, beta-stabilized chromium alkyls, has been synthesized and tested for catalytic activity in ethylene polymerization. Although not active alone, these compounds do exhibit remarkable activity when reacted with a partially dehydroxylated high surface area carrier. The best supports seem to be fluorided alumina or the aluminophosphates, depending on the particular chromium alkyl being tested. The worst was always silica. Both divalent and tetravalent chromium alkyls were tested and found to have high catalytic activity. Comparisons of activity and polymer structure were made between these compounds and previously studied organochromium compounds with pi-bonded ligands.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 32 (1981), S. 467-478 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Einflußgrößen für das Aufkohlungsverhalten von Chrom-Nickel-Stählen und -Legierungen in Gasen bei hohen TemperaturenDie Arbeit behandelt das Korrosionsverhalten einer Reihe von handelsüblichen sowie einfachen Modellegierungen mit hohem Chrom- und Nickel-Gehalt in aufkohlenden Gasen mit niedriger Sauerstoffaktivität bei Temperaturen zwischen 825 und 1000°C. In den verwendeten Gasgemischen aus Wasserstoff und Methan wurde der Einfluß unterschiedlicher Kohlenstoffaktivitäten (0,3 und 0,8) durch Verändern des Methananteils im Gemisch untersucht. Der Oberflächenzustand der Proben und sein Einfluß auf die Aufkohlung wurde als Variable berücksichtigt; dazu wurden die Oberflächen nach Standardmethoden vorbehandelt.Die Kinetik des Korrosionsprozesses wurde mit Hilfe von herkömmlichen gravimetrischen Techniken untersucht; zusätzlich wurde mit Hilfe von Mikrogefügeuntersuchungen an Querschnitten geprüft, welche Faktoren die Verschlechterung der Werkstoffeigenschaften bei der Aufkohlung in erster Linie verursachen. Der Einfluß der Temperatur und der Kohlenstoffaktivität des Gases wurde besonders berücksichtigt; außerdem wurden wichtige Werkstoffparameter wie metallurgischer Zustand, Zusammensetzung und Oberflächenzustand auf ihre Bedeutung für die Vorgänge geprüft.
    Notes: The paper is concerned with the corrosion behaviour of a range of commercial and simpler “model” high chromium-nickel alloys exposed to gaseous carburising environments of low oxygen activity, at temperatures within the range 825°C to 1000°C. H2-CH4 mixtures have been used and carbon activities of 0.3 and 0.8 studied by varying the proportion of CH4 in the mixture. The surface condition of the specimens and its effect upon carburisation behaviour has been investigated as a variable by the use of standardised surface preparation techniques.The kinetics of the corrosion process have been studied by the use of conventional gravimetric techniques and cross-sectional microstructural examinations have aided in establishing the factors of primary importance in the degradation of materials by carburisation. The contributions made by the temperature and carbon activity of the gaseous environment have been highlighted and the important material variables such as metallurgical form, composition and surface condition have been investigated in order to evaluate their significance.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 1811-1836 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A model for the crystallization kinetics of polymers is outlined and is used to interpret observations of the crystallization of polyethylene at high pressures. This model introduces a distinction between σe the lamellar surface energy which controls the lamellar thickness, and σe′, the surface nucleus surface energy which controls the growth rate. Differential scanning calorimetry and electron microscopy data for several polyethylenes crystallized at pressures of up to 8 kb are presented. From the dependence of lamellar thickness on the crystallization undercooling at 5 kb, it is found that σe increases markedly with pressure leading to the formation of very thick crystals at high pressures. The magnitude of the increase in σe is in agreement with σe values calculated from the dependence of melting temperatures on pressure. The nucleus surface energy σe′ is not expected to vary significantly with pressure, and estimates of growth rates of 5 kb which indicate that the growth rate does not vary significantly with pressure at constant under-cooling confirm this. Fractionation effects and the differences in behavior between different polyethylenes are also discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 647-655 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: D,L-Leucine-NCA and D,L-methionine-NCA were copolymerized in varying mole fractions by using primary base initiation. The methionine segments were oxidized to both sulfoxide and sulfone functions by using peroxide oxidation. The compositions of the resulting polymers were established with the aid of 60 MHz NMR. The transport properties of aqueous solutes through membranes formed from these polymers were studied by means of a diffusive dialysis measurement. The transport of NaCl, urea, creatinine, uric acid, and bacitracin were found to be strongly dependent on the degree of hydration of the polymers. The relative rates of transport of these solutes were affected by interaction with the polymers, when the degree of hydration was not excessive. The degree of hydration was a function of the extent of methionine oxidation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 5 (1967), S. 791-795 
    ISSN: 0006-3525
    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
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