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  • 1
    Electronic Resource
    Electronic Resource
    Polarization mechanisms in phase II poly(vinylidene fluoride) films (1983)
    s.l. : American Chemical Society
    Macromolecules 16 (1983), S. 60-68 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00235a012
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    High pressure melting and crystallization of Nylon-11 (1985)
    Springer
    Journal of materials science 20 (1985), S. 1753-1762 
    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 Differential thermal analysis (DTA), high pressure differential thermal analysis (HP-DTA), and high temperature X-ray studies are combined to elucidate the origin of the two melting peaks in Nylon-11. The results of the studies suggest that two species of crystals are involved in the melting of Nylon-11 for samples crystallized at atmospheric pressure or when the environmental pressure is below 4 kbar. At atmospheric pressure, the high melting species is predominant. However, under hydrostatic pressures, the high melting species undergoes phase transition to the low melting species before melting. The amount of the material involved in the transition depends on the pressure. At pressures of 4 kbar or greater, the entire high melting species transforms to the low melting species. The melting behaviour, at atmospheric pressure, of samples crystallized at high pressures also shows two melting peaks if the crystallization pressure is below 4 kbar. The amount of the low melting species increases with increasing pressure and, at 4 kbar or higher, only melting of the low melting species is observed. The X-ray photographs taken at room temperature suggest that samples crystallized between atmospheric pressure and 3 kbar contain both theα-form and theδ′-form crystals but the samples crystallized at 4 kbar and higher contain only theα-form crystal. However, it appears from X-ray scans taken at high temperatures near melting that the low melting species is of theδ-form and the high melting species of the δ′-form crystals for samples crystallized below 4 kbar. Theδ-form crystals result from theα-δ transition that occurs at 95° C. Moreover, the melting at high pressures (〈4 kbar) of samples crystallized at atmospheric pressure also appears to involve aδ′-δ transition. These results suggest that both the crystal forms,δ andδ′, are stable at high temperatures, if the environmental pressure is below 4 kbar, and that only theδ-form crystals are stable up to melting at pressures greater than 4 kbar.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00555281
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  • 4
    Electronic Resource
    Electronic Resource
    The interaction between a penny-shaped crack and a spherical inhomogeneity in an infinite solid under uniaxial tension (1991)
    Springer
    Acta mechanica 90 (1991), S. 91-104 
    Details
    ISSN: 1619-6937
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary This paper presents an approximate three-dimensional analytical solution to the elastic stress field of a penny-shaped crack and a spherical inhomogeneity embedded in an infinite and isotropic matrix. The body is subjected to an uniaxial tension applied at infinity. The inhomogeneity is also isotropic but has different elastic moduli from the matrix. The interaction between the crack and the inhomogeneity is treated by the superposition principle of elasticity theory and Eshelby's equivalent inclusion method. The stress intensity factor at the boundary of the penny-shaped crack and the stress field inside the inhomogeneity are evaluated in the form of a series which involves the ratio of the radii of the spherical inhomogeneity and the crack to the distance between the centers of inhomogeneity and crack. Numerical calculations are carried out and show the variation of the stress intensity factor with the configuration and the elastic properties of the matrix and the inhomogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01177402
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Effect of simple stress on the glass transition of polymers at high pressures (1986)
    Springer
    Journal of materials science 21 (1986), S. 2901-2907 
    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 Experimental studies, which have been carried out in this laboratory, showed the yield strength in tension, compression, and shear in the rubbery and the glassy states increased with increasing hydrostatic pressure. Moreover, the Young's modulus also increased with pressure and the amount of the increase across the glass transition temperature (T g) at a given pressure can be as large as three orders of magnitude in the case of elastomers. An extension of the Gibbs-Dimarzio theory is proposed to account for the effect of applied stress on the glass transition temeprature of glass-forming polymers. When a simple stress, such as tensile, compressive or shear stress, is applied to a polymer, the T g will decrease, compared to a polymer without applied stress. A glass-forming polymer in the vicinity of the transition would behave differently from that predicted by rubber elasticity. The partition function taking into account the effect of stress is suggested to be $$\Gamma = \Sigma W(f, n_0 ){\text{ }}\exp {\text{ }}[ - \beta (PV + U - \sigma V\varepsilon )]$$ where the strain ɛ=σ (f − f 0) in which f and f 0 are the fraction of flexed bonds with and without stress, respectively. Furthermore, by this model, the Young's modulus across the transition, E L and E G, can be evaluated. The Young's modulus increases with increasing pressure at lower and moderate pressure range but the increase is rather small at very high pressure range.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00551509
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  • 7
    Electronic Resource
    Electronic Resource
    Physical ageing of polypropylene in glassy state (1989)
    Springer
    Journal of materials science 24 (1989), S. 3613-3615 
    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 Physical ageing behaviour of a semicrystalline polymer, polypropylene, has been studied at a pressure-temperature state (P=2.5 kbar,T=15° C) for which the amorphous region is in the glassy state. Polypropylene contains 57% crystallinity and its glass transition temperature at atmospheric condition is −20° C. The ageing behaviour was monitored by measuring the Young's modulus (E) from the stress-strain curves as a function of ageing time up to 200 h. The Young's modulus of the rapidly pressure quenched samples increased at 0.4% per ageing hour of the initial value for up to 30 h and tapered off thereafter. The glassy polypropylene also exhibited a memory behaviour when it was given a pressure perturbation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02385747
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  • 8
    Electronic Resource
    Electronic Resource
    High pressure X-ray studies of polymers (1977)
    Springer
    Journal of materials science 12 (1977), S. 1793-1797 
    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 A systematic study was made on polyethylene at high pressures and elevated temperatures using X-ray diffraction. Polyethylene with an initial chain-folded morphology and the orthorhombic crystal structure did not transform to any other phase before melting at the temperature and pressure used. Crystallization, however, at high pressures producing extended-chain crystals gave rise to either a new crystal phase, probably hexagonal, or the orthorhombic phase, depending on the crystallization conditions. A reversible solid-state phase transformation was observed between the orthorhombic and hexagonal phases. None of the previous interpretations put forward to account for the high pressure DTA and dilatometric studies of polyethylene, would appear to be appropriate in view of these findings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566239
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  • 9
    Electronic Resource
    Electronic Resource
    An X-ray study of polyethylene at pressures up to 14 000 kg cm−2 at 298 K (1977)
    Springer
    Journal of materials science 12 (1977), S. 771-778 
    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 diamond piston-anvil method was used to make X-ray wide-angle diffraction studies of polyethylene at 298 K and at pressures up to 14 000 kg cm−2. The data obtained were compared with the results of a study by Ito and Marui, and their observations (which were made at pressures up to 3000 kg cm−2) were essentially confirmed. However, our data revealed that the linear compressibility in the [1 1 0] and [2 0 0] directions did not vary with pressure in a linear fashion over the entire range, and the empirical relation-ε hk l =A h k lρ − B hk lρ 2, where ε h k l is the stress on h k l planes, was not found to be adequate for the planes (1 1 0) and (2 0 0) for pressures up to 14 000 kg cm−2. With the addition of a third cubic term C h k lρ3 to the relation, a better fit of the data could be achieved. By ignoring strains in the chain direction, the volumetric strains as a function of pressure were calculated, and the data agreed well with the equation of state derived by Pastine for the crystalline phase of polyethylene. A value for the Grüneisen constant γ 0 at atmospheric pressure and 298 K was calculated and a value γ 0=3.64 was obtained. This agrees well with values obtained by Ito and Marui, No phase transition was observed at 298° C for the pressure range reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00548170
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  • 10
    Electronic Resource
    Electronic Resource
    High pressure X-ray studies of polymers. I. Calibration for the diamond-anvil cell in the range 0 to 15 kbar (1977)
    Springer
    Journal of materials science 12 (1977), S. 1064-1068 
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540996
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