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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1579-1584 
    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: New methods for rapidly obtaining elastic modulus and density measurements during isothermal polymer aging are given. The elastic measurements are performed using a Rockwell hardness tester. In this case, the elastic recovery is measured. Rapid density measurements are performed using a “double drop” density gradient columan method. Here, a fully aged and a freshly quenched specimen are dropped simultaneously into the column. Simultaneous column height differences directly measure the density difference of the two specimens. The results of these two experiments extend previously reported aging measurements to relatively low times of aging. A log (time) law for both properties is found to the smallest times measured.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 770-785 
    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
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 776-781 
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1064-1070 
    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
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 4183-4197 
    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: A self-seeding technique, coupled with isothermal crystallization, was used to prepare isotactic polypropylene specimens of varying spherulite size, but of constant crystallinity and lamellar thickness. The latter quantities were also varied by changing the isothermal crystallization temperature. The electrical lifetime at constant applied voltage, in a point-plane geometry, was measured. It was found that the electrical lifetime decreased with increasing spherulite size and, more weakly, with decreasing crystallinity (at a given spherulite size).
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 6
    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
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  • 7
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 5 (1984), S. 215-223 
    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: The voltage lifetime of a poly(ethylene terephthalate)/glass composite is measured for two different orientations of short fiber with respect to the applied electric field (perpendicular and parallel). The difference in the voltage lifetime between two configurations is attributed to the microstructural features at the (fiber/matrix) interface, particularly microvoids. The morphological observations by scanning and transmission electron microscopy (SEM, TEM), and optical microscopy reveal the presence of microvoids as well as the crazed matrix and consequent erosion channel. The tree initiation site is identified and the nature of tree propagation is explained. A theoretical model based on such microstructural features is constructed, which explains the voltage lifetime vs fiber orientation in a relative framework. It is concluded that the graseous discharge at microvoids is the main mechanism for electrical breakdown and the site of such gaseous discharge is the (fiber/matrix) interface. Therefore, the orientation dependence of the electrical breakdown is the geometrical effect of the interface voiding with respect to the direction of the applied electric field.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 3 (1982), S. 18-28 
    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: Two sheet molding compounds, one containing 65 weight percent E-glass fiber and no filler (SMC-65) and the other containing 50 weight percent glass and 15 weight percent CaCO3 filler were subjected to sinusoidal, load-control, tension-tension fatigue. The macroscopic behavior showed some notch sensitivity for both materials, but particularly for SMC-65. The extent of failure damage over the specimen length decreased with decreasing load amplitude. Different failure mechanisms appear to operate under high- and low-cycle fatigue conditions. Microscopic surface damage studies at stresses near the endurance limit showed several stages in the fatigue failure. For SMC-65, these stages are, sequentially, matrix crack initiation and growth, matrix pulverization, fiber fracture, and fiber pullout. A similar, but less distinct pattern was observed for SMC-50. Acoustic emission was also followed during fatigue cycling near the endurance limit. Distinct amplitude distribution peaks for each failure process were seen. It is suggested that matrix fracture, permanent deformation and Euler buckling are all important in high cycle fatigue failure.
    Additional Material: 26 Ill.
    Type of Medium: Electronic Resource
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