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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2591-2616 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microstructural changes occurring during the process of crystallization in as-spun poly(ethylene terephthalate) (PET) have been monitored using wide- and small-angle X-ray scattering, optical birefringence, shrinkage measurements, and specific gravity.Shrinkage and birefringence results show a competition between two processes: chain re-coiling on the one hand and crystallization on the other hand. A consistent correlation among WAXS, SAXS, shrinkage, and birefringence results is demonstrated. SAXS data show a fibrillar morphology. On the basis of WAXS results, the crystallization is envisioned as a two stage process: first, the formation of defective fibrils, and then the formation of more perfect crystals. WAXS results also demonstrate a remelting phenomenon in samples which have experienced positive shrinking.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1-14 
    ISSN: 0887-6266
    Keywords: poly (p-phenylene terepthalamide) ; Kevlar® ; heat treatment ; structure development ; mechanical properties ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The evolution of several structural characteristics during isothermal heat treatment of poly(p-phenylene terephthalamide) was studied. In this work, heat treatment was interrupted after different treatment times, with the specimens immediately quenched to room temperature. These specimens were then characterized by tensile testing, wide- and small-angle x-ray scattering, and optical microscopy. Structural parameters obtained from these measurements relate to crystal perfection (via the paracrystalline axial distortion parameter), axial crystallite size, transverse crystallite size, degree of chain misorientation, and degree of pleating. Structural and mechanical parameters were then plotted against heat-treatment time to obtain kinetic isotherms for each parameter. The kinetics of the removal of chain misorientation parallels that of tensile modulus increase under all conditions. Of the other structural parameters, only the kinetics of pleat removal mimics that of modulus change, indicating that pleat removal is the effective cause of increased chain alignment and thereby of increased axial stiffness. ©1995 John Wiley & Sons, Inc.
    Additional Material: 27 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 125-133 
    ISSN: 0887-6266
    Keywords: mechanical deformation ; PET ; high-temperature deformation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanical properties of poly(ethylene terephthalate) (PET) fibers at temperatures above the glass transition are investigated by means of a specially constructed device. Measurements of the deformation rate and of the “dynamic” stress-strain curves of the fibers are performed in nearly isothermal regime (after initial rapid heating) in a temperature interval 100-200°C. The results reported in the present work demonstrate that the high-temperature mechanical characteristics of rapidly crystallizing polymers can be deduced to a satisfactory precision, while keeping the crystallinity development at low level. Our investigations indicate that if the high-temperature deformation is sufficiently fast, the polymer behavior is similar to the deformation at sub-Tg temperatures. Based on this similarity, a qualitative model of the deformation in the high-temperature region is proposed. The proposed model is fundamentally equivalent to the models describing mechanical deformation of glassy polymers at temperatures below the glass transition. ©1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 16 (1995), S. 284-287 
    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 surface composition and energy of carbon fiber has been carefully analyzed and quantified. Untreated, AU, surface-treated, AS, and heat-treated AHT fibers were all studied. AS fiber was surface-treated by an electrolytic oxidation process. AHT fiber was heat-treated at elevated high temperatures under vacuum. X-ray photoelectron spectroscopy (XPS or ESCA) was used to investigate the surface elemental concentration of carbon fibers. The corresponding surface free energies of these fibers were calculated from the contact angles measured by a dynamic contact angle analyzer. Results showed a strong correlation between the surface treatment and heat-treatment history and the surface chemistry of carbon fibers. After oxidation treatment, the surface free energy was increased by adding functional group elements (oxygen and nitrogen). However, these added elements could be removed by high temperature treatment under vacuum. The diffusion of O, N, and Na was discussed. The correlation between oxygen and nitrogen concentration and carbon fiber surface free energy has been plotted. These fibers would be used to quantify the relationship between carbon fiber surface free energy and the interfacial shear strength of the fiber-polymer interface.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 10 (1989), S. 222-225 
    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: This paper explores the possibility of using X-ray micro-analysis for studying the morphology of the polymer blend composite PPS(GF)/HDPE (glass-filled poly(phenylene sulfide)/high density polyethylene) system and the characterization of filler and polymer dispersion in the system.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 11 (1990), S. 201-210 
    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: Determination of the degree of crystallinity of the matrix of polymer matrix composites by wide-angle X-ray diffraction is discussed. An extensive theoretical review is given, and many of the practical difficulties are also discussed. Poly(aryl ether ether ketone)-carbon fiber composites are used as example materials. It is shown that although wide-angle X-ray diffraction is potentially useful for unoriented samples, there are practical and theoretical difficulties in applying the technique to highly oriented materials.
    Additional Material: 15 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
    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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  • 9
    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: Microscopic observations of thermoplastic poly(ethylene terephthalate) reinforced with short E-glass fibers revealed a unique matrix microstructure influenced by the orientation of densely packed glass fibers. The observed platelets tend to surround a fiber in a cylindrical sheath pattern. This observation of the crystalline platelet morphology is possible by the combination of ion-etching and the shadowing effect of protruding fibers.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 10
    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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