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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 211 (1966), S. 514-515 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Striking evidence in favour of the concept that bulk polymers may also consist largely of lamellar-like crystals has been obtained from a study of the crystallization behaviour of isotactic polypropylene. Samples of this material were first compressed in a high-pressure mould to 60,000 lb./in.2 and ...
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 350 (1991), S. 563-563 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Recycled plastics often possess relatively poor mechanical properties in comparison with products made from virgin materials. In particular, recycled plastic packaging materials are derived largely from polyolefins of low strength, weakened further by impurities in the recycled feedstock. ...
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 493-509 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of thermal treatment at temperatures in the 177-250°C. range for 2 hr. on solution-grown single crystals of poly-4-methylpentene-1 have been studied by using electron microscopy. Crystals were grown both from 0.02% pentyl acetate solution at 110°C. and from 0.02% toluene solutions at temperatures less than 80°C. A number of distinct types of crystals have been obtained in the same or in separate solutions depending on the crystallization conditions. These crystals have some morphological characteristics in common such as a square outline with well-defined faces. The contrasting features include such things as a marked difference in relative size, with the smaller crystals showing extensive overgrowth and collapse markings. Observations by means of differential scanning calorimetry (DSC) on the melting behavior of these various crystals show the presence of distinct and characteristic melting points. The effects of a given thermal treatment depend on the type of crystals used, with the larger crystals showing greater stability. The first effects are the appearance of lines, notches at the edges, and holes. An increase in temperature results in an increase in these effects with the formation of fibrillar structures. Consideration is given to the influence of molecular conformation and molecular chain folding on the observed results.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1987-1997 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The effects of thermal treatment in the 70-90°C. region on polybutene-1 crystals, prepared by precipitation from dilute pentyl acetate solutions and with lath, hexagonal, and square morphologies, have been studied by using electron microscopy. The stability of polybutene-1 crystals to thermal treatment increases in the order: lath 〈 hexagonal 〈 square. Elucidation of the crystallographic directions in unheated lath crystals with respect to the overall morphology was carried out; evidence for restricted folding in these crystals is discussed.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1651-1667 
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The plastic deformation of poly-4-methylpentene-1 (P4MP1) crystals on a unidirectionally drawn substrate has been investigated by electron microscopy. In addition to cracks spanned by fibrils and buckling perpendicular to the stretch direction, both features found in deformation studies of other polymers, a unique slip mechanism leading to sectorization of P4MP1 crystals is observed; deformation was also found to occur by means of localized lamellar thinning. The exact type of plastic deformation occurring in P4MP1 crystals is found to depend on the orientation of the lamellae with respect to the tensile axis. Some evidence for a periodicity on the fibrils studied is given.
    Additional Material: 15 Ill.
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  • 6
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Fatigue tests in reversed tension-compression have been carried out on samples of polyethylene and polystyrene of widely varying molecular weights, extending up to 2, 000, 000. All tests on polystyrene specimens were made at 1600 rpm. For polyethylene, tests speeds had to be reduced to 100 rpm in order to avoid serious temperature effects. For both materials, increasing molecular weight leads to improved resistance to alternating loading. For polystyrene, this improvement in ultimate properties even continued well beyond molecular weight values where Tg, becomes effectively independent of molecular weight. For polyethylene, samples of high molecular weight did not fail even after 107 cycles of alternating loading at a stress level of 3000 psi.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: A series of polished polystyrene specimens, coated with silicone oil, were tested in tension and in tension-compression fatigue cycling at 21 Hz. Oils of four different viscosities, ranging from 5 cSt to 1000 cSt, were utilized. The craze initiation stress and the tensile fracture stress both increased with the increase of oil viscosity. For the 1000 cSt oil, the stress-strain curve was essentially the same as that of an uncoated sample. The average lifetime to fracture in the fatigue tests depends upon the stress amplitude and on the oil viscosity. For the 1000 cSt oil, the fatigue behavior is similar to that of uncoated samples, except at high imposed stresses, where lifetime is somewhat lower. For the low viscosity oil, the average lifetime is from one to two decades less than for uncoated samples. Discussion is given of the influence of stress amplitude and oil viscosity on the test results and on the morphology of the fracture surfaces.
    Additional Material: 11 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 14 (1974), S. 801-805 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Fatigue tests under reversed tension-compression have been made on polystyrene specimens in both the unnotched and notched condition. For the notched specimens subject to a stress amplitude of 2500 psi, the log of the fatigue life was found to be a linear function of the log of the notch size. From the data, it was possible to determine an inherent flaw size for polystyrene subject to alternating loading and this value is compared to corresponding values obtained from static tests. Fracture surfaces were examined by scanning electron microscopy and the changes produced by notching are discussed.
    Additional Material: 6 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 519-526 
    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: Significant improvements in the fatigue life of polystyrene can be realized by increase in molecular weight. In this investigation, samples of polystyrene of varying molecular weight were subject to alternating cycles of axial tension and compression at a test speed of 1600 rpm. One set of fatigue tests was made on samples machined from commercial whole polymer rod. A second set of samples was prepared from a PS standard having an average molecular weight of 160,000 and a narrow molecular weight distribution. A third set of samples had a high average molecular weight of 860,000. For a whole polymer, the S-log N curves tended to have the same general shape as for metals, and the endurance limit appeared to be about 1400 psi. The test results show that the average fatigue life, at any given stress amplitude, is significantly increased by increase in molecular weight. For example, the average life of the high molecular weight standard at any given stress level was found to be more than tenfold that of the low molecular weight standard.
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Letters 4 (1966), S. 453-458 
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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