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  • 11
    Electronic Resource
    Electronic Resource
    The flow of solid polymers under high pressure (1974)
    Springer
    Colloid & polymer science 252 (1974), S. 680-695 
    Details
    ISSN: 1435-1536
    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: Zusammenfassung Die Deformation und Fließeigenschaften fester Polymerer unter uniaxialer Spannung und unter Druck wurden für eine Serie von kristallinen wie amorphen Polymeren bei Drucken bis 7 kb gemessen. Für einige Polymere, wie das Polytetrafluoräthylen, wird Kaltverstreckung bei steigendem Druck ausgelöst und Elektroscanning-Bilder zeigen, daß die örtliche plastische Deformation stark reduziert ist. Die wahre Fließspannung und Bruchspannung jedoch steigen beide mit dem Druck, ebenso der Elastizitätsmodul. Der Anstieg ist am größten im niedrigen Druckbereich unter 2kb. Dieses Verhalten ist einer durch den Druck initiierten Verlagerung einer Tief-temperatur-β′-Umwandlung zuzuschreiben. Der Einfluß der Polymerkomposition und der anfangs elastischen Konstanten auf die Druckabhängigkeit des elastischen Moduls und der Fließspannung wird diskutiert. Das beobachtete Verhalten läßt sich in Termen der Enddehnungseffekte und einem druckabhängigen Fließkriterium diskutieren. Es wird gezeigt, daß einige amorphe Polymere eine durch den Druck ausgelöste spröd-duktil-Umwandlung erfahren. Und diese Feststellungen wurden verwendet, die hydrostatische Extrusion von Polyimid und Polysulfon bei Raumtemperatur zu erklären.
    Notes: Summary The deformation and flow properties of solid polymers under uniaxial tensile and compressive loading have been determined for a variety of both crystalline and amorphous polymers at hydrostatic pressures to about 7 , kb. For some polymers, like polytetrafluoroethylene, cold drawing is inhibited by increasing pressure, and scanning electron micrographs show that local plastic deformation is greatly reduced. However, the true flow stress and the true fracture stress both increase with pressure, as does, also, the elastic modulus. The increase is greatest in the low-pressure range below 2 kb. This behavior is attributed to the pressure-induced shifting of a lowtemperatureβ′-transition. The influence of polymer composition and of the initial elastic constants on the pressure dependence of the elastic modulus and the yield stress is discussed. The observed behavior can be analyzed in terms of finite strain effects and a pressure-dependent yield criterion. It is shown that some amorphous polymers undergo a pressure-induced brittle-ductile transition, and these findings are used to explore the hydrostatic extrusion of polyimide and polysulfone at room temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01554493
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  • 12
    Electronic Resource
    Electronic Resource
    Interior Morphology of Bulk Polypropylene (1966)
    [s.l.] : Nature Publishing Group
    Nature 211 (1966), S. 514-515 
    Details
    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 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/211514a0
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  • 13
    Electronic Resource
    Electronic Resource
    The dynamic mechanical properties of high polymers at low temperatures (1958)
    Springer
    Algebra universalis 1 (1958), S. 114-158 
    Details
    ISSN: 1420-8911
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02189648
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  • 14
    Electronic Resource
    Electronic Resource
    Fatigue of polymers (1980)
    Springer
    International journal of fracture 16 (1980), S. 499-532 
    Details
    ISSN: 1573-2673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Résumée On passe en revue la nature générale de la rupture dans les polymeres lorsqu'ils sont sujets à des contraintes alternées en contraste par rapport à des contraintes statiques on croissantes de manière régulière. On discute également les mécanismes moléculaires et les aspects micromécaniques qui prennent place dans le processus de rupture par fatigue. Une attention particuliere est accodée à la fatigue thermique où les résultens de fatigue résultent principalement d'une élévation sensible de la température de l'éprouvette en raison du chauffage par hystérèse. Cependant,l'accent est principalement consacré à la fatigue mécanique dans lequel la rupture est le résultat d'un amorçage et d'une propagation d'une fissure tels qu'ils resultent de la nature périodique des charges appliquées. On accorde une attention particulière à des variables importantes internes ou caractéristiques du matériau telles que la structure du polymère, le poids moléculaire, les liaisons et le type et contenu des agents de dilution. Des variables externes significatives telles que la contrainte ou 1'amplitude du facteur d'intensité de contrainte, la contrainte moyenne, la température, la fréquence et l'environnement sont également pris en considération. Des méthodes variées susceptibles d'être utilisées en vue d'accroitre de manière significative la résistance à la fatigue des polymères sont mis en avant et sont discutés.
    Notes: Abstract The general nature of fracture in polymers, when subject to alternating loads as distinct from static or steadily increasing loads, is reviewed; and the molecular mechanisms and micromechanics aspects of the fatigue fracture process are discussed. Some attention is given to thermal fatigue, where fracture results primarily from a large specimen temperature rise due to hysteresis heating. However, primary emphasis is devoted to mechanical fatigue, in which fracture is a result of initiation and propagation of a crack, as a result of the periodic nature of the applied load. Attention is given to the important internal, or material, variables such as polymer structure, molecular weight, crosslinking, and filler or diluent type and content; and to significant external variables such as stress or stress intensity factor amplitude, mean stress, temperature, frequency and environment. Various methods that can be utilized to provide significant degrees of enhancement in the fatigue resistance of polymers are outlined and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02265215
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  • 15
    Electronic Resource
    Electronic Resource
    Deformation and fracture behavior of polystyrene ionomer and ionomer blends (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 652-658 
    Details
    ISSN: 1435-1536
    Keywords: Deformation ; fracturebehavior ; polystyreneionomers ; ionomerblends ; microstructure of theionomer ; ioncontent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The deformation and fracture behavior of sulphonated polystyrene ionomers, and of blends of these with polystyrene have been investigated. The microstructure of the ionomer, which varies with ion content, appears to have a significant effect on mechanical properties. Both tensile strength and toughness increase appreciably at ion contents near 5 mol%, where clusters become dominant over ion pairs and multiplets. In blends of the ionomers and polystyrene, phase separation occurs and the ionomer component appears in the form of fine particles dispersed in the polystyrene matrix. These particles possess a greater effective entanglement density than the matrix, as a result of ionic crosslinking, and they provide reinforcement against early craze breakdown and fracture. Tensile strength and fracture energy increase rapidly as the ionomer concentration in the blend is increased and they become essentially independent of blend ratio above about 10 wt% of the ionomer. Tests carried out on thin film specimens of the blends show that the dispersed ionomer particles adhere well to the matrix and contribute to the fracture energy both by inducing matrix crazing and by internal fibrillation within the particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00654041
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  • 16
    Electronic Resource
    Electronic Resource
    Environmental effects of silicone oil on mechanical properties of low and high molecular weight PMMA (1984)
    Springer
    Journal of materials science 19 (1984), S. 3967-3975 
    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 The influence of a silicone oil environment on deformation modes and tensile behaviour of poly(methylmethacrylate) were investigated. Tests were made on samples coated with oils of varying viscosity, ranging from 5 to 1000 cSt. To investigate the effects of polymer molecular weight on environmentally induced craze growth and stability, tests were conducted on an extruded grade of relatively low molecular weight and on a cast grade of high molecular weight. All of the silicone oils acted as crazing agents and tensile strength and ductility were reduced in value as the viscosity of the oil was lowered. The low molecular weight polymer failed in a brittle manner in all environments but developed earlier and more intensive crazing as the liquid viscosity was reduced. The high molecular weight material underwent a ductile-brittle transition when the environment was changed from air to low viscosity silicone oils. The flow of the oil into existing flaws and crazes was sufficiently impeded at 1000 cSt viscosity so that both necking and surface crazing were observed under these conditions. To illustrate the various deformation and fracture modes that were observed, micrographs of free and fracture surfaces are presented and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00980760
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  • 17
    Electronic Resource
    Electronic Resource
    Effects of thermal history on isotactic polypropylene (1968)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 12 (1968), S. 1901-1919 
    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: The effect of past thermal history on the melting behavior of isotactic polypropylene is investigated in some detail. It is shown that a series of stepwise annealing treatments at steadily increasing temperatures will raise the final melting point and will result in a double endothermic peak if the final anneal temperature is at or close to 160°C. It is also shown that a series of stepwise annealing treatments at steadily decreasing temperature will lead to multiple DSC peaks. The number of such separate peaks is equal to or greater than the number of annealing steps. Even low-temperature anneals (100-130°C) affect the melting endotherm, while high-temperature anneals have a marked effect on both the degree of crystallinity of the sample and the final melting temperature. For a 3-min anneal, the highest degree of crystallinity is produced by an anneal temperature of 155°C. The highest melting temperature (∼182°C) is produced by a 30-min, or longer, anneal at about 160°C. The implications of these results in terms of crystal thickening and perfection are discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1968.070120811
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  • 18
    Electronic Resource
    Electronic Resource
    Low-temperature mechanical relaxations in polymers containing aromatic groups (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 1097-1115 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Studies have been made of the secondary relaxation processes in the solid state of a number of polymers containing aromatic groups in the polymer chain. The polymers investigated include one, polystyrene, with the aromatic group in side-chain positions, and six high polymers in which phenylene rings lie in the main backbone chain. In polystyrene, wagging and torsional motions of the side chain phenyl rings give rise to a low-temperature δ-relaxation which is centered at 33°K (1.7 Hz) and which has an activation energy of about 2.3 kcal/mol. Most of the polymers with phenylene rings in the main chain exhibit a low-temperature relaxation in the temperature region from 100°-200°K. This relaxation process is centered at 159°K (0.54 Hz) in poly-p-xylylene, at 162°K (0.67 Hz) in polysulfone, and at 165°K (1.24 Hz) in poly(diancarbonate). In poly(2,6-dimethyl-p-phenylene oxide), two overlapping low-temperature relaxations are found, one in the range 125-140°K and the other near 277°K (ca. 1 Hz). The low-temperature secondary relaxation process in all of these polymers is believed to be associated with local reorientational motion of the phenylene, or substituted phenylene, rings or with combined motion of the phenylene rings and nearby chain units. For these low temperature relaxation processes, the activation energy is about 10 kcal/-mole. The temperature location of the relaxation appears to depend on the specific units to which the phenylene rings are attached and on steric and polar effects caused by substituents on the ring. In the poly-p-xylylenes the relaxation is shifted to much higher temperatures by a single Cl substitution on the ring but remains at essentially the same temperature position when dichlorosubstitution is made. The effects of water on the magnitude and temperature location of the observed low temperature relaxations, as well as the implications of the study for other polymers containing aromatic groups in their backbone chains, are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.160090607
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  • 19
    Electronic Resource
    Electronic Resource
    Influence of rubber content on static and dynamic properties of polystyrene (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 69-76 
    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: Mechanical properties, deformation modes under both uniaxial tension and compression, low temperature mechanical relaxation behavior, and resistance to fracture under dynamic loading have been investigated for a medium impact grade of polystyrene, Shear yielding is the dominant mode of plastic deformation in compression while matrix crazing, together with some tearing and cavitation of the rubber phase, occurs in tension. The craze microstructure, as determined by transmission electron microscopy (TEM), is typical of that noted in polystyrene, with sharp craze-bulk interfaces and a characteristic midrib section. The presence of a third phase, possibly a processing aid, is evident in the TEM scans and in the dynamic mechanical data. The present data, together with the data obtained on polystyrene and on high impact polystyrene, are used to show the strong influence of rubber content on various mechanical properties, such as the tensile craze yielding stress, ductility, compression yield strength, degree of strain softening, and fatigue durability.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290112
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  • 20
    Electronic Resource
    Electronic Resource
    Influence of polar and nonpolar plasticizers on the mechanical properties of a sulfonated polystyrene Ionomer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1291-1294 
    Details
    ISSN: 0887-6266
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: No abstract.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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