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  • 1985-1989  (7)
  • 1987  (3)
  • 1986  (4)
Material
Years
  • 1985-1989  (7)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 265 (1987), S. 193-205 
    ISSN: 1435-1536
    Keywords: Poly(TMPS) ; in situ ; SAXS ; crystallization ; kinetics
    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 isothermal crystallization kinetics of poly(TMPS) has been measured by ISSAXS and results obtained for a molecular weight fraction (21,000) below the critical entanglement molecular weight (25,000) and another one above it (371,000). The SAXS intensity vs. time curves suggest that a single transformation mechanism exists. The SAXS long period is independent of crystallization time for both poly(TMPS) fractions. However the interlamellar thickness contribution to the long period is dependent upon molecular weight and crystallization temperature, increasing with temperature and molecular weight. The crystallite contribution also increases over the range studied. Both fractions exhibit a significant, but reversible decrease in thickness on cooling the sample from the crystallization temperature to room temperature and recyling again. The change is more pronounced for 371,000 specimen in keeping with its lower crystallinity. The path dependence of lamellar dimensions has significant implications in the morphological characterization of polymers annealed or crystallized at one temperature and then measured at another one.
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 1631-1643 
    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 cold-drawing behavior of naturally aged poly(ethylene terephthalate) (PET) is investigated and an attempt is made to compare the mechanical behavior of unaged commercial PET and material which has been naturally aged for 11 years. Mechanical, viscometric, DSC and IR measurements are applied. The previously observed unusual ability of fresh PET bristles to be cold drawn up to 15:1 is not achieved for the naturally aged material. This fact is related to chemical cross-linking occurring on the surface of bristles after drawing and thermal treatment. The cross-linked skin is unsoluble, infusible, and uncrystallizable. The natural aging defeats the ability of PET to respond to external treatments which would otherwise change the internal structure. Such a “stabilization” of material properties is a result of the transformation, during natural aging, of the original physical network into a chemical network consisting of covalent bonds.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 651-661 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small- and intermediate-angle (0.006 〈 Q 〈 0.25 Å) neutron scattering experiments have been performed on polyethylene terephthalate (PET). Amorphous and semicrystalline samples with deuterated PET molecular weights of 24,200 and 40,500 were prepared. The average value of RGW/MW1/2 determined in the small-angle region for the amorphous samples is 0.406, in close agreement with the experimental θ-solvent (0.398-0.420) and theoretical (0.394) values for unperturbed dimensions. The intermediate-angle results for the amorphous sample are consistent with the random coil prediction to Q = 0.08 Å, but beyond this Q value there is some deviation from Gaussian behavior. The semicrystalline samples show a decrease in the radius of gyration as measured in the small-angle region and an increase in intensity (when compared to the amorphous data) in the intermediate-angle region, especially for the low-molecular-weight material. These results suggest that crystallization in PET is accompanied by greater molecular reorganization than has previously been observed in most bulk polymers.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2617-2630 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Small- and wide-angle X-ray scattering (SAXS and WAXS), shrinkage, and density experiments were performed on poly(butylene terephthalate) fibers which had been isothermally crystallized at different temperatures, and at constant tension, for times ranging from 100 to 1050 ms.A consistent correlation among WAXS, SAXS, and the kinetic results is demonstrated. Shrinkage results show that the crystallization process prevails over the chain-re-coiling process. Density measurements show that the rate of crystallization increases with temperature. Pinhole X-ray photos show that the orientation of the chains within the crystals remains constant with time and temperature. WAXS diffractometer scans show the development of wide-angle Bragg peaks.SAXS shows the development of small-angle Bragg peaks, as the annealing time is increased. The two-lobe arced pattern is the characteristic pattern. The value for long spacing ranged from 100 to 120 Å, increasing with temperature.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thin layers of (25-1000 Å) tin were evaporated onto a highly oriented polypropylene sheet. Two rates of deposition were used: 5 and 20 Å/s. For the more rapid deposition rate, a preferred orientation of tin was found in all cases. Here, the Sn a axis lay parallel to the polymer chain (polymer c axis). The same orientation relationship was found for the slower deposition rate, but only at lower Sn film thicknesses; at the higher film thicknesses, a random orientation of crystallites is found. Scanning electron micrographs show an equiaxed tin grain structure for the case of no preferred orientation and a platelet morphology for the case of preferred orientation, the thin dimension of the platelets lying perpendicular to the polymer chain axis. Although no clearcut evidence either for or against crystallographic epitaxy has been found, a plausible case for geometrical epitaxy is presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 2591-2616 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Microstructural changes occurring during the process of crystallization in as-spun poly(ethylene terephthalate) (PET) have been monitored using wide- and small-angle X-ray scattering, optical birefringence, shrinkage measurements, and specific gravity.Shrinkage and birefringence results show a competition between two processes: chain re-coiling on the one hand and crystallization on the other hand. A consistent correlation among WAXS, SAXS, shrinkage, and birefringence results is demonstrated. SAXS data show a fibrillar morphology. On the basis of WAXS results, the crystallization is envisioned as a two stage process: first, the formation of defective fibrils, and then the formation of more perfect crystals. WAXS results also demonstrate a remelting phenomenon in samples which have experienced positive shrinking.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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