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  • Polymer and Materials Science  (36)
  • Kevlar®  (1)
  • Morphology  (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
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Transient effects in the crystallization of polyethylene (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 821-827 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A specimen of linear polyethylene was subjected to isothermal secondary crystallization at a series of temperatures below the primary isothermal crystallization temperature, the melting and primary crystallization stages being held constant throughout the investigation. Dilatometric measurements exhibit an S-character at low values of undercooling Tp - Ts, where Tp and Ts are, respectively, the primary and secondary crystallization temperatures, whereas at larger undercooling, an initial very rapid crystallization is followed by a very slow stage. When corrected for thermal contraction of the polymer, the net degree of secondary transformation is seen to peak at a temperature about 5°C below Tp. The S-character of the isotherms and the peaked temperature variation of degree of transformation lead to the conclusion that a large portion of the secondary crystallization consists of the nucleation and growth of the new crystallites. Johnson-Mehl-Avrami analysis leads to a model of heterogeneous nucleation within the remaining amorphous zones, followed by one-dimensional, diffusion-controlled growth.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.160070507
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  • 7
    Electronic Resource
    Electronic Resource
    Time-dependent effect of spherulite size on the tensile behavior of polypropylene (1970)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 1871-1877 
    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 mechanical behavior of isotactic polypropylene following primary crystallization is known to be dependent on the aging time (e.g., at room temperature). This aging time effect is believed to be related to a form of additional crystallization (sometimes called secondary crystallization). We show in the present work that the aging characteristics depend on spherulite size and that indeed the spherulite size effects reported by others very likely reflect chain rearrangements upon aging, rather than some property associated with the as-crystallized material.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1970.070140720
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetics of fiber heat treatment. I. Experimental apparatusWork supported by the National Science Foundation under Grant No. CPE 8304058. (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 2689-2693 
    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
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300632
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of diethylene glycol content and annealing temperature on the structure and properties of poly(ethylene terephthalate)Work supported by the U. S. National Science Foundation, under Grant No. INT-8206731, and by the Bulgarian State Committee on Scientific and Technological Progress. (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 32 (1986), S. 3371-3392 
    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 2,2′-oxydiethanol (diethylene glycol, DEG) content (ranging from 2 to 15 mol %) and of the annealing temperature (in the range from 100 to 260°C) on the density, calorimetric, dynamic- and static-mechanical and small angle X-ray scattering (SAXS) behavior of undrawn and drawn samples (granules, films, and bristles) of poly(ethylene terephthalate) (PET) has been studied. The known dependences on the annealing temperature are confirmed. Some discrepancies with earlier investigations of the dependences on the DEG content are established: constant values for the SAXS intensity and long spacing, for the lamellar thickness and for the volume fraction crystallinity ac. These discrepancies are explained by the variation of the glass transition temperature (Tg) and melting temperature (Tm) of the materials with different DEG contents. The previous hypothesis of the segregation of the comonomer (DEG) units into the amorphous regions is confirmed.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070320202
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  • 10
    Electronic Resource
    Electronic Resource
    Dependence of electrical breakdown on spherulite size in isotactic polypropylene (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 4183-4197 
    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: A self-seeding technique, coupled with isothermal crystallization, was used to prepare isotactic polypropylene specimens of varying spherulite size, but of constant crystallinity and lamellar thickness. The latter quantities were also varied by changing the isothermal crystallization temperature. The electrical lifetime at constant applied voltage, in a point-plane geometry, was measured. It was found that the electrical lifetime decreased with increasing spherulite size and, more weakly, with decreasing crystallinity (at a given spherulite size).
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291248
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