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  • 1
    Electronic Resource
    Electronic Resource
    The influence of microstructure on the failure behaviour of PEEK (1989)
    Springer
    Journal of materials science 24 (1989), S. 4538-4544 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study, different molecular weight PEEK materials were used to determine the effect of spherulite size on fracture. Melt processing of the PEEK at different temperatures produced samples of different average spherulite size. A permanganic etching technique was used to reveal the spherulites. It was found that for low molecular weight 150P PEEK, the spherulite size increased with melt processing temperature; but, for the higher molecular weight 450G PEEK, the spherulite size remained approximately constant. Also, the average spherulite size was markedly lower for the material of higher molecular weight. The failure behaviour of these samples was studied using a compact tension test. It was found that the fracture toughness of PEEK varied with processing temperature. Also, the average spherulite size of a PEEK material had a profound influence on the fracture mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00544542
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  • 2
    Electronic Resource
    Electronic Resource
    The influence of microstructure on the failure behaviour of PEEK (1990)
    Springer
    Journal of materials science 25 (1990), S. 3746-3752 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this study, different molecular weight PEEK materials were used to determine the effect of spherulite size on fracture. Melt processing of the PEEK at different temperatures produced samples of different average spherulite size. A permanganic etching technique was used to reveal the spherulites. It was found that for low molecular weight 150P PEEK, the spherulite size increased with melt processing temperature; but, for the higher molecular weight 450G PEEK, the spherulite size remained approximately constant. Also, the average spherulite size was markedly lower for the material of higher molecular weight. The failure behaviour of these samples was studied using a compact tension test. It was found that the fracture toughness of PEEK varied with processing temperature. Also, the average spherulite size of this material had a profound influence on the fracture mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00575414
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  • 3
    Electronic Resource
    Electronic Resource
    ESR measurements during γ-radiation induced solid-state polymerization of 1,3,5-trithianeThis work was supported by the National Science Foundation. (1976)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 177 (1976), S. 835-843 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Während der durch γ-Strahlen ausgelösten Festkörperpolymerisation von 1,3,5-Trithian zu Polythiomethylen wurden ESR Spektren aufgenommen. Die Reaktion wurde bei mehreren Temperaturen, jeweils unter Luft und N2, durchgeführt. Während die ursprüngliche Kinetik in beiden Fällen zweiter Ordnung ist, wird bei den höchsten Temperaturen unter Luft eine niedrigere Ordnung beobachtet. Massenspektrographische Ergebnisse zeigen spontane Zersetzung unter diesen Hochtemperaturverhältnissen. Es wird geschlossen, daß der beobachtete Peak bei Auftragung der Reaktionsgeschwindigkeit gegen die Temperatur auf den Beginn des spontanen Kettenabbruchs zurückzuführen ist.
    Notes: The time-dependences of ESR spectra were measured during the γ-radiation induced solid-state polymerization of 1,3,5-trithiane to polythiomethylene. The reaction was carried out at several temperatures, both under air and under N2. The initial reaction kinetics are second order, but become of lower order at the highest temperatures under air. Mass spectrographic results indicate spontaneous degradation under these high temperature conditions. It is concluded that an observed peak in reaction rate with temperature derives from the onset of spontaneous chain termination.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1976.021770321
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  • 4
    Electronic Resource
    Electronic Resource
    Morphology and barrier properties of oriented blends of poly(ethylene terephthalate) and poly(ethylene 2,6-naphthalate) with poly(ethylene-co-vinyl alcohol) (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 680-692 
    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: Morphology and oxygen permeability studies were carried out for blends of poly(ethylene terephthalate), PET, and poly(ethylene 2,6-naphthalate), PEN, with poly(ethylene-co-vinyl alcohol), EVOH. PET/EVOH blends are seen as a possible substitute for poly(vinylidene chloride)-coated PET packaging films. The effects of several processing parameters such as draw temperature and draw ratio on blend morphology and barrier properties suggest that the morphology of the EVOH phase dictates to a large extent the oxygen permeabilities of these blends. The relationships between morphology and oxygen permeability and explained are explained by consideration of two-phase conduction models. The model of Fricke is found to be a good predictor of the barrier properties of the PET/EVOH system. The oxygen permeability of PET was reduced by a factor of 4.2 with the addition of 20 wt% EVOH and that of PEN by a factor of 2.7 with the addition of 15 wt% EVOH. Water vapor permeabilities and mechanical properties of PET and PEN were only slightly affected by the addition of 15 wt% EVOH.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350808
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  • 5
    Electronic Resource
    Electronic Resource
    Anomalous two-stage spherulite growth in poly(aryl ether ketones) during isothermal crystallization (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 3095-3105 
    Details
    ISSN: 0887-6266
    Keywords: crystallization ; spherulite ; anomalous growth ; poly(aryl ether ketones) ; optical microscopy ; SALS ; SAXS ; lamellar structure ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Anomalous two-stage spherulite growth has been observed in poly(aryl ether ketones) during isothermal crystallization. The first stage consists of a conventional growth with Maltesecross pattern at a lower growth rate. The morphology shows a smooth interface, dense structure and negative birefringence. The second stage grows in the form of “aggregate” at a higher rate. The morphology shows an open dendrite structure without preferred optical orientation. The second morphology is also termed the “overgrowth.” The occurrence of overgrowth is favored only near the maximum growth rate region and diminishes in the slow growth region. The transition of the two-stage growth is attributed to the change of growth direction of the constituent lamellae. We have confirmed this by microbeam small-angle light-scattering measurements. The lamellar structures in both growth stages were followed by time-resolved small-angle synchrotron x-ray scattering. It was found that the lamellar structures of the crystals formed at both stages are the same. A possible explanation for the two-stage growth is the interface breakdown caused by large perturbations of local composition and/or stress fields. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Solidification of semicrystalline polymers using a variable interface temperature model (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 471-483 
    Details
    ISSN: 0887-6266
    Keywords: solidification ; semicrystalline polymers ; interface temperature ; spherulites ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solidification of semicrystalline materials often occurs in significantly undercooled melts. The crystal growth process in such melts is convoluted due to the fact that the interface between the solid and liquid domains of the microscopic crystals is at an unknown temperature. However, it is possible to let the temperature of this interface be unspecified and solve the problem with a semianalytical method if the growth velocity is prescribed. Solutions for the temperature profiles in both solid and liquid phases are presented in this work, along with the interface temperature, for phase change processes controlled by the kinetics of crystallization rather than diffusion processes, which is typical for polymers. The method is used for one-dimensional problems in cartesian, cylindrical, and spherical geometries that correspond to commonly found microstructures. It is found that the temperature of the interface is significantly below the equilibrium melting point and a quasi steady-state regime is reached rapidly. Comparison with the classical Neumann's solution shows that the temperature profiles are similar but the position of the interface differs considerably. © 1996 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of flow rate and temperature on crystallization kinetics, crystallinity index, and elastic modulus of PEEK (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 655-666 
    Details
    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: Dynamic, in situ wide angle X-ray scattering (WAXS) studies of the melt crystallization of injection-molded poly(ether ether ketone) (PEEK) have been carried out using an X-ray diffractometer and a position-sensitive detector. A test cell has been fabricated to fit inside the diffractometer and yet work as a complete injection molding apparatus. The rate of crystallization has been shown to increase with decreasing crystallization temperature and/or increasing flow rate in the mold. The crystallization rate decreases dramatically with increase in melt soak time at 400°C. The crystallinity index, which affects the stiffness, toughness, and fracture behavior of PEEK, has been measured under various processing conditions, by wide angle X-ray scattering, so as to optimize the process parameters: molding time, mold temperature, melt temperature, soak time at melt temperature, and flow rate. It has been shown that the crystallinity and hence the elastic modulus increase with increase in crystallization temperature and/or flow rate. Chain orientation has been shown to be absent in the bulk of the injection-molded specimens under normal molding conditions.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380406
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  • 8
    Electronic Resource
    Electronic Resource
    Polyamides and polyesters with improved mechanical properties (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 575-581 
    Details
    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: An attempt is made to establish the most proper initial structure for the obtaining of highly drawn (at room temperature) nylons and polyesters. It is found that neither the completely crystalline structure nor the fully amorphous one but a low-crystallinity, very imperfect structure (with a large number of small crystallites) is the most suitable one. Through ultraquenching of nylon 6 and PBT melts, and storage at ambient conditions, draw ratios of 7 and 8, respectively, are achieved. Subsequent annealing results in the obtaining of doubly higher values of the elasticity modulus and tensile stress. By means of WAXS, SAXS, IR spectroscopy, and DSC measurements the obtained structure is characterized. The highly drawn and annealed samples show a strongly reduced concentration of chain folds and a lack of long spacing.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420302
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of blend rheology on the transport property of oriented poly(ethylene terephthalate) blends (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1749-1759 
    Details
    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: Rheological studies were performed to delineate appropriate stretching windows, and poly(ethylene terephthalate)/poly(ethylene-co-vinyl alcohol) blend films were extruded biaxially within such processing windows. The morphology and oxygen permeability properties of these films, with and without a compatibilizer, were characterized. The intent of this study was to achieve a blend oxygen permeability value (OPV) of less than 1. At a fixed draw ratio and draw temperature, appropriate rheological matching could lead to an increase in the aspect ratio of the EVOH phase and, thereby, of oxygen barrier properties. This study concludes that by melt viscosity matching it is not possible to obtain blends with OPV of less than 1. The model of Fricke, used to predict blend permeability, was found to be more accurate at the higher draw temperatures, with the measured values deviating increasingly negatively from the predicted values as the draw temperature is decreased. © 1995 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070561306
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  • 10
    Electronic Resource
    Electronic Resource
    Kinetics of strain-induced crystallization during injection molding of short fiber composites of poly(ether ether ketone) (1991)
    Brookfield, Conn. : Wiley-Blackwell
    Polymer Composites 12 (1991), S. 169-178 
    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: Crystallization kinetics of short glass and carbon fiber composites of poly(ether ether ketone) (PEEK) under melt-strain conditions have been obtained for the first time, using in-situ wide angle X-ray scattering, and have been correlated to a model based on the Avrami equation in order to enable minimization of the processing time for injection molding of these materials. It has been demonstrated that increased flow rate of the melt in the mold and, consequently, increased shear rate accelerates the crystallization process of PEEK composites, analogous to similar trends observed previously in PEEK resin. Short glass fiber composites of PEEK crystallize slower than the resin under identical processing conditions, while short carbon fiber composites crystallize faster than the resin, except at the highest mold temperatures and the lowest flow rates. A model based on the Avrami equation has been proposed to fit the kinetics data obtained experimentally. The Avrami coefficient has been calculated and Arrhenius plots have been used to predict the crystallization kinetics at temperatures lower than those at which experimental data have been obtained here. Fiber orientation, flexural elastic modulus, and flexural fracture toughness of the composites have also been evaluated.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pc.750120306
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