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  • Chemistry  (33)
  • Physics  (19)
  • Lamellar Crystals  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Transmission electron microscope observations of fibrillar-to-lamellar transformations in melt-drawn polymers — I. Isotactic polypropylene (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 294-300 
    Details
    ISSN: 1435-1536
    Keywords: Polypropylene ; Fibrillar Crystals ; Lamellar Crystals ; Morphology ; Transition
    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 transformation during heat treatment from a fibrillar to a lamellar morphology in highly oriented polypropylene is followed by transmission electron microscopy (TEM) and small angle electron scattering (SAES). While the as drawn films exhibit long (up to 1μm) continuous fibrillar crystals, those crystals disintegrate into short crystalline blocks which finally aggregate into a lamellar morphology during the heat treatment. After even longer heat treatment the lamellar crystals start to thicken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410467
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  • 2
    Electronic Resource
    Electronic Resource
    Meaning and measurement of crystallinity in polymers: A Review (1969)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 9 (1969), S. 331-338 
    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: A useful concept in polymer science is the degree of crystallinity - the fraction of the polymer that exists in a relatively ordered state. Methods of determination of the degree of crystallinity using density, infrared, thermal, N.M.R. and X-ray measurements are examined in light of modern notions of the structure of semi-crystalline polymers.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760090504
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  • 3
    Electronic Resource
    Electronic Resource
    The physical aging of isotactic polypropyleneResearch sponsored by the U.S. Army Research Office under Grant No. DAAG2979-G-0187. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 776-781 
    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: 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
    URL: http://dx.doi.org/10.1002/pen.760211206
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  • 4
    Electronic Resource
    Electronic Resource
    Environmental testing of a glass-fiber-reinforced thermoplastic (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 1064-1070 
    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: 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
    URL: http://dx.doi.org/10.1002/pen.760241312
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  • 5
    Electronic Resource
    Electronic Resource
    Microstructural aspects of failure in semicrystalline polymers (1984)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 24 (1984), S. 770-785 
    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: 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
    URL: http://dx.doi.org/10.1002/pen.760241007
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  • 6
    Electronic Resource
    Electronic Resource
    Rapid measurements of elastic modulus and density in polypropylene sheet during aging (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1579-1584 
    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: 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
    URL: http://dx.doi.org/10.1002/app.1981.070260513
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  • 7
    Electronic Resource
    Electronic Resource
    Consolidation of high-modulus PET laminates and the role of chemical healing (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 113-126 
    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: In this work, a process for making high-modulus (8GPa) laminates of poly(ethylene terephthalate) (PET) has been developed. Oriented films of the polymer were produced by a technique utilizing a very high extension rate, and these films were crossplied and consolidated to form the product laminates. The procedures for drawing the original film lamina and consolidating the laminates were optimized with respect to the material properties. Further, the possibility of chemical healing-bonding of the lamina together by chemical reaction, not diffusion-was investigated for these materials. It was found that laminates could be formed with both high moduli and strong interply bonding and that the moduli actually increase due to crystallization during pressing. Longrange diffusion during bond formation was ruled out, since crosslinked polyesters were found to bond as readily as uncrosslinked. Chemical reactions between contacted surfaces appear to be a likely mechanism of bonding.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400110
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  • 8
    Electronic Resource
    Electronic Resource
    Lamellar and interlamellar structure in melt-crystallized polyethylene. I. Degree of crystallinity, atomic positions, particle size, and lattice disorder of the first and second kinds (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 243-276 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An x-ray diffraction method for the simultaneous determination of crystallinity (including intracrystalline defects), effective Debye-Waller factors, and atomic positions has been developed and applied to semicrystalline polyethylene. It was found that this material unambiguously constitutes a two-phase system. Measurements of intracrystalline lattice disorder in the chain direction and perpendicular to the chain direction show these to be in the ratio 1:2.5. Lattice disorder was principally of the first kind. Paracrystalline disorder in the [110] direction was less than 2.4% at all experimental conditions. Results include measurements of degree of crystallinity, particle size, space group, and unit cell parameters and variation of these quantities with crystallization temperature, ambient temperature, and time.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080205
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  • 9
    Electronic Resource
    Electronic Resource
    Lamellar and interlamellar structure in melt-crystallized polyethylene. II. Lamellar spacing, interlamellar thickness, interlamellar density, and stacking disorder (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 9 (1971), S. 85-114 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the small-angle scattering power and the degree of crystallinity in melt-crystallized high-density polyethylene have been used to evaluate the “amorphous” density in situ by the relation, \documentclass{article}\pagestyle{empty}\begin{document}$ (2\pi/V)\int_0^\infty {S\tilde g} (S)dS = (\rho_{\rm c} - \rho_{\rm a})^2 \upsilon_{{\rm er}} (1 - \upsilon_{{\rm er}}) $\end{document} where V is the irradiated volume and ḡ(S) is the “slit-smeared” absolute intensity. The amorphous density is a function of sample history and is always higher than the extrapolated melt density. After slit-height correction, and within the experimental error, the ratio of the two observed long periods is 2:1 at all temperatures (25--126°C). The lamellar thickness and the average interlamellar spacing are obtained from the degree of crystallinity and the first corrected long period. At increasing temperatures between 25°C and 110°C, the lamellae become thinner while the interlamellar zone expands by almost half. Over this range the changes are reversible with temperature. Above 110°C, both the lamellae and the interlamellar region expand with temperature. The thickening is partially reversible upon recooling. Other results obtained include measurements of stacking disorder and of microstructural changes with crystallization temperature and with time at ambient temperature.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.160090107
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and mechanical properties of highly oriented poly(ethylene terephthalate) films (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 964-970 
    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: The relationships between the supermolecular structure of poly(ethylene terephthalate) films subjected to cold drawing and subsequent zone annealing and their mechanical properties are investigated. The effectiveness of zone annealing is compared to that of annealing with fixed ends. Microstructural changes occurring during heat treatment and zone annealing are monitored using wide angle X-ray scattering, small angle X-ray scattering, infrared spectroscopy, differential scanning calorimetry, and static mechanical tests. The very high modulus and strength of the zone-annealed films are directly attributed to the large number of the molecules connecting the crystallites.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321408
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