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  • Polymer and Materials Science  (2,586)
  • Cell & Developmental Biology  (705)
  • 1985-1989  (1,833)
  • 1980-1984  (1,458)
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Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 26 (1988), S. 1271-1286 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Random copolymers of ethylene with 1-butene, 1-octene, and 1-octadecene have been prepared using a homogeneous vanadium-based catalyst system. Comonomer contents determined by 13C-NMR analysis of polymer solutions are in the range 1-10 mol%. Crystallinities were estimated by means of density measurements, x-ray diffraction, differential scanning calorimetry, laser Raman spectroscopy, and CPMAS 13C-NMR spectroscopy. The results are compared with those obtained for heterogeneous copolymers of ethylene containing 1-4 mol% 1-butene. As the comonomer content is increased, the crystallinity decreases. The dimension perpendicular to the 110 plane in orthorhombic crystallites decreases linearly with crystallinity. This decrease in crystallite size is accompanied by an increase in the size of the orthorhombic unit cell. For copolymers containing large amounts of 1-octene and 1-octadecene, a second crystalline form appears. Differences in estimates of crystallinity are discussed in terms of looser packing in highly branched copolymers and the extent to which the second crystalline form participates in the phase structure.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 131 (1985), S. 145-155 
    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: The application of electron irradiated polypropylene granulate as a nucleating agent in extrusion has recently been suggested. This article discusses the chemical characterisation of such an electron treated granulate. Since the irradiation is carried out under atmospheric conditions, the relationship between decomposition, crosslinking and oxidation products has been determined. Oxidation is confined principally to the outermost molecular layers and leads to the formation of carbonyl groups via peroxide intermediates. As well as specific group tests, ESCA has been used to measure the degree of oxidation and for indirect determination of vinyl groups after bromination.
    Notes: In jüngster Zeit wird der Einsatz von elektronen-bestrahltem Polypropylengranulat als Nukleierungsmittel bei der Extrusion vorgeschlagen. Die vorliegende Arbeit beschäftigt sich mit der chemischen Charakterisierung der elektronen-bestrahlten Granulate. Da die Bestrahlung unter atmosphärischen Bedingungen stattfindet, werden nicht nur der Zusammenhang von Abbau und Vernetzung, sondern auch Oxidationsprodukte bestimmt. Die oxidative Schädigung findet hauptsächlich in den oberen Moleküllagen statt und führt über peroxidische Zwischenprodukte zur Entstehung von Carbonylgruppen. Neben für funktionelle Gruppen spezifischen Nachweismethoden wird die oberflächen-spezifische ESCA-Methode zur Erfassung des Oxidationsgrades und zur indirekten Vinylgruppenbestimmung nach der Bromierung eingesetzt.
    Additional Material: 1 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 203-217 
    ISSN: 0148-7280
    Keywords: α-chlorohydrin ; antifertility agent ; ram ; sperm metabolism ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The effects of the male antifertility agent, α-chlorohydrin, six of its derivatives, and glycidol were studied on the metabolism of washed ram spermatozoa in vitro with fructose as substrate. The α-chlorohydrin derivatives were the amino, the phosphorylated, and four glycol-bridge (ketal) compounds. All compounds except glycidol, in a concentration between 0.1 and 100 mM, reduced the aerobic glycolsis and/or oxidation of fructose. However, there was not a high correlation between the ability of these compounds to inhibit the metabolism of ram spermatozoa in vitro and their antifertility activity when administered to male rats. Other factors are clearly involved in their antifertility activity, eg, the concentration of the compounds in the epididymis and their conversion of either more or less spermicidal compounds in the body.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2817-2834 
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal degradation behavior of poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) was investigated with the aid of some appropriate model compounds. The pyrolysis products of these materials were identified by gas chromatography (GC), gas chromatography/Fourier transform infrared spectroscopy (GC/FT-IR), and gas chromatography/mass spectrometry (GC/MS). The residual chars were characterized by IR spectroscopy. Thermogravimetric analysis (TGA) was applied to study the effect of end-group concentration on the degradation characteristics of the two polyamides. Kinetic parameters that describe the thermal degradation of the polyamides were also evaluated by TGA. The results of this investigation suggest that the thermal decomposition of these aromatic polyamides involves homolytic as well as hydrolytic cleavages of the amide units.
    Additional Material: 13 Ill.
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  • 5
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The supermolecular structures of polyethylene filaments prepared by crystallization from solution in extensional flow at different crystallization temperatures as well as of annealed and zone-drawn samples have been characterized by means of X-ray diffraction methods. The lattice distortions in the crystallites of such samples are quantitatively determined for the first time. The results show that a direct correlation between the crystallite dimensions and the amount of lattice distortions on the one hand and the axial Young's modulus on the other hand can be excluded. Based on X-ray, mechanical and shrinkage investigations, some parameters of the structure of the non-crystalline regions are estimated. A structure model for the high-modulus polyethylene filaments is discussed.
    Notes: Die übermolekulare Struktur scherkristallisierter PE-Fäden unterschiedlicher Kristallisationstemperatur sowie getemperter und zonengereckter Proben wird mittels Röntgenbeugung charakterisiert. Erstmalig an derartigen Fäden werden die Gitterstörungen in den Kristalliten quantitativ angegeben. Die Ergebnisse zeigen, daß ein direkter Zusammenhang zwischen den Kristallitgrößen und dem Ausmaß der Gitterstörungen einerseits und dem axialen E-Modulandereseits ausgeschlossen werden kann. Auf Basis von Röntgen-, Modul- und Schrumpfmessungen werden Abschätzungen zum Aufbau der ungeordneten Bereiche durchgeführt und daraus Modellvorstellungen zur Struktur hochmoduliger PE-Fäden mitgeteilt.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 37 (1986), S. 557-563 
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Blown films of LD-PE prepared with varying processing conditions have been investigated using different X-ray diffraction methods. All films have a-texture. Differences in the degree of orientation are noticed. Arragement and size of lamellae are estimated by SAXS-investigations. A WAXS peak separation procedure using Pearson-VII-functions allows the determination of crystallite sizes. The orthorhombic modification as the dominant crystalline phase and some amount of monoclinic modification of PE have been detected from the resolved WAXS pattern.
    Notes: Blasfolien aus LD-PE unterschiedlicher Herstellungsparameter wurden komplex röntgenographisch untersucht. Alle Folien bestizen eine a-Textur. Unterschiede in der Texturgüte werden angegeben. SAXS-Untersuchungen ermöglichen Aussagen zur Lamellenanordnung und -größe. Eine Peak-Separation der WAXS mittels Pearson-VII-Funktionen erlaubt Kristallitgrößenangaben und läßt monokline Anteile neben der hauptsächlich auftretenden orthorhombischen Modifikation erkennen.
    Additional Material: 7 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 7 (1983), S. 79-88 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: There are two major fire processes, an understanding of which is essential for effective fire safety design: (1) the conditions under which a combustible material may become involved in flaming combustion, and (2) the rate at which such a material, once involved, will provide an output of heat, smoke, toxic gases, etc., which can endanger people and property. The first process may be regarded as covering both ignition and spread of fire on materials; its complement is the way in which fire may become extinguished. It is necessary for such processes to bring in a characteristic of the basic combustion reaction which, directly or indirectly, expresses the reactivity of the combustion process. Thus pilot ignition is usually associated with an approximate surface fuel temperature. More basically, it is associated with a critical flow rate of volatiles and a critical heat loss from the flame, the latter being influenced by ambient oxygen and temperatures conditions as well as heat lost and gained by the fuel itself. The most important factor governing the production of dangerous product is the rate at which volatiles first (fuel controlled fires) and later air (air controlled fires) are fed into the flames. The reactivity is of less importance, although it may be one of the factors which control combustion efficiency. In general, the more efficient is the combustion the more heat is produced, but the less smoke and toxic gases are produced. Some of the main advances in the above areas are reviewed in this paper.
    Additional Material: 2 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 1 (1989), S. 399-400 
    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: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 147-162 
    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 fusion welding behavior of a medium density polyethylene resin has been studied for a wide range of heating rates using a recently developed test methodology. With this method, the thermal and physical phenomena occurring at the interface of two thin polyethylene pieces assembled by fusion can be studied. It consists of a thermal welding phase and a phase of mechanical separation of the welded assembly. For the mechanical phase, an adaptation of the T-peel test was used. These conditions make it possible to determine the thermal welding parameters (temperature, time) for optimal mechanical quality of the joint, according to a criterion established by optimization of the peel test used. The variations in minimum temperature required for an optimum weld, as a function of heating rate, can be simulated with a numerical model based on the concept of macromolecular interdiffusion. Consistent with the experimental behavior, the numerical model involves two parameters characteristic of the diffusion behavior of the polyethylene resin. Thus, these parameters characterize the weldability of the polyethylene resin under study.
    Additional Material: 8 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 4959-4969 
    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: Structure property relationship of four different diisocyanates is studied in detail. The isocyanates selected are TDI, MDI Crude, HDI, and IPDI. Physical properties such as mechanical, dynamic mechanical, electrical, and thermal are studied. Dynamic mechanical analyses are based on the compound resonance principle. Among all, IPDI-based polymer showed mediocre trend and TDI-based polymer showed best properties.
    Additional Material: 4 Ill.
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