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  • Chemical Engineering  (16)
  • Gitterdefekte  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Wachstumsdefekte in polymeren Nadelkristallen (1981)
    Springer
    Colloid & polymer science 259 (1981), S. 241-246 
    Details
    ISSN: 1435-1536
    Keywords: Polystyrol ; Nadelkristalle ; Gitterdefekte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary Lattice defects in polymeric needle crystals (shish) were investigated. The length of the crystals depends on preparation conditions and may vary between 0.1μm and severalμm. Density fluctuations exist along the individual needle crystals. The wave length of the fluctuation is controlled by the chemical nature of the polymer and its amplitude by preparation and annealing conditions. The wave length of the density fluctuations may vary from 90 Å to 300 Å. Needle crystals from isotactic polystyrene additionally exhibit (001) grain boundaries. The orientation relationship of adjacent grains along a needle corresponds to a 180° rotation of the lattice around the molecule axes. The molecular nature of that grain boundary is discussed.
    Notes: Zusammenfassung Die Gitterdefekte in polymeren Nadelkristallen (shish) werden untersucht. Die Länge eines Nadelkristalles kann je nach Herstellungsart.zwischen 0.1μm und mehrerenμm variieren. In den einzelnen Nadelkristallen bilden sich längs der Nadelrichtung Dichteschwankungen aus. Die Schwankungslängen hängen in der Hauptsache von der Polymerart ab, während die Amplituden der Schwankung von der thermischen Vorgeschichte abhängen. Die Schwankungslängen sind zwischen 90 Å und 300 Å. In Nadelkristallen aus isotaktischem Polystyrol sind zusätzlich (001)-Korngrenzen vorhanden. Die Orientierung beider Kristallgitter entspricht einer Rotation von 180° um die Molekülachse. Ursachen für diesen Typ von Korngren zen werden diskutiert.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01381767
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  • 2
    Electronic Resource
    Electronic Resource
    Fracture behavior of oriented poly(ether-ether-ketone) (PEEK) (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 405-414 
    Details
    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: Poly(ether-ether-ketone) (PEEK) is a newly developed engineering thermoplastic with potentially vast application in advanced composites due to its exceptional performance. It is thus desired to understand the relationship between physical processing, microstructure and fracture in this semicrystalline polymer. Both oriented and unoriented PEEK were mechanically characterized using static test of three-point bend specimens. The molecular chain orientation was imposed using a rolltrusion technique. The effects of thickness, strain rate, Initial crack length ratio, and orientation on fracture toughness (Kc) are investigated. The crystallinity is also examined by density measurement. The degree of orientation is determined qualitatively by wide-angle X-ray scattering diffraction patterns and quantitatively by further measurement using an image analysis system. Fractographic analysis, using scanning electron microscopy, provides precise information about the mode of fracture, Results indicate that both the modulus and the fracture toughness are remarkedly increased in the direction of drawing (T-type) as opposed to the transverse direction (L-type).
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290609
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of crystallization in high-speed spinning (1991)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 31 (1991), S. 661-666 
    Details
    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: Removal of the heat of fusion during steady-state crystallization in a high-speed spinline places restrictions on the morphology of the crystallites. An appropriate model is that of a thermal dendrite. It is shown that for this case there exists at each temperature along the threadline a limiting growth velocity, beyond which heat cannot be conducted away fast enough to permit growth. It is suggested that crystallization occurs when a fluid element reaches a temperature at which heat can just be conducted away rapidly enough. Comparison of dendrite theory predictions with experimental values of crystallite diameter and crystallization temperature shows satisfactory agreement. Poly(ethylene terephthalate) has been taken as the example.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760310907
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  • 4
    Electronic Resource
    Electronic Resource
    Structure and mechanical properties of highly oriented poly(ethylene terephthalate) films (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 964-970 
    Details
    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: The relationships between the supermolecular structure of poly(ethylene terephthalate) films subjected to cold drawing and subsequent zone annealing and their mechanical properties are investigated. The effectiveness of zone annealing is compared to that of annealing with fixed ends. Microstructural changes occurring during heat treatment and zone annealing are monitored using wide angle X-ray scattering, small angle X-ray scattering, infrared spectroscopy, differential scanning calorimetry, and static mechanical tests. The very high modulus and strength of the zone-annealed films are directly attributed to the large number of the molecules connecting the crystallites.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321408
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  • 5
    Electronic Resource
    Electronic Resource
    Meaning and measurement of crystallinity in polymers: A Review (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 331-338 
    Details
    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 useful concept in polymer science is the degree of crystallinity - the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X-ray measurements are examined in light of modern notions of the structure of semi-crystalline polymers.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760090504
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  • 6
    Electronic Resource
    Electronic Resource
    Microstructural aspects of failure in semicrystalline polymers (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 770-785 
    Details
    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: Microstructural features of semicrystalline polymers are reviewed, as are the roles of chain properties and thermal history in their development. Experimental results relating failure properties to microstructural detail are described. General models to explain inter- and intra-spherulitic failure behavior are proposed. Important are (a) the role of spherulite size in boundary incompatibility, (b) competition between spherulite boundary cracking and intraspherulitic yielding, (c) competition between localized (interspherulitic) fracture and dispersed (intraspherulitic) fracture.
    Additional Material: 26 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241007
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  • 7
    Electronic Resource
    Electronic Resource
    The physical aging of isotactic polypropyleneResearch sponsored by the U.S. Army Research Office under Grant No. DAAG2979-G-0187. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 776-781 
    Details
    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: The microstructural changes in isotactic polypropylene (PP), subsequent to quench from the melt to around Tg were studied using dynamic mechanical loss, volume dilatometry, small and wide angle X-ray scattering, infrared and NMR spectroscopy. The β-transition loss tangent and the specific volume decreased linearly with logarithm of aging time. Dynamic mechanical loss and NMR spectroscopy results established that amorphous chain mobility reduced during aging. X-ray and IR techniques showed that the crystallinity, the crystalline density, and the average chain conformation do not change during aging. Tensile tests indicated that diffusion of air or moisture into the polymer is not a competitive mechanism for the aging phenomenon. A simple free-volume model is quantitatively consistent with these observations. The fraction of the material which cannot age increased as the quench temperature decreased. Further, at lower temperatures a portion of the nonageable fraction is shown to reside in the amorphous fraction.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211206
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  • 8
    Electronic Resource
    Electronic Resource
    Meaning and measurement of crystallinity in polymers: A Review (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 452-460 
    Details
    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 useful concept in polymer science is the degree of crystallinity - the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X -ray measurements are examined in light of modern notions of the structure of semi -crystalline polymers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760090612
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  • 9
    Electronic Resource
    Electronic Resource
    Environmental testing of a glass-fiber-reinforced thermoplastic (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1064-1070 
    Details
    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: Stress-corrosion data for poly(ethylene terephthalate) reinforced with short glass fibers are provided under various environments and the microscopic observations are compared with the lifetime data. It is concluded that the lifetime behavior coincides with the microstructural features; this aspect is quantified by the statistical analysis.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760241312
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  • 10
    Electronic Resource
    Electronic Resource
    Stress-rupture lifetime of a poly(ethylene terephthalate)/glass composite under an alkaline solution environmentResearch supported by the University-Industry Research Program, Center for Composite Materials (1984)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 5 (1984), S. 208-214 
    Details
    ISSN: 0272-8397
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Stress corrosion testing of injection molded, short-fiber (E-glass) reinforced poly(ethylene terephthalate) (PET), in a 10 weight percent NaOH solution, indicated that a PET-matrix degradation mechanism was operating. This is in direct contrast to the fiber degradation observed in acidic (10 weight percent HCl solution) stress corrosion tests on this material. Stress-rupture lifetime in the alkaline solution was shorter than that in the acidic solution, suggesting that the alkaline attack on the PET matrix is more aggressive than the acidic attack on the E-glass fibers. In both environments, fiber/matrix interface deterioration was also observed. Alkaline lifetime versus toughness behavior has been analyzed by established statistical methodology, using the empirical lifetime expression and the Weibull distribution function.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750050309
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