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  • 1
    Electronic Resource
    Electronic Resource
    The effect of crystallinity on chain mobility and free volume in the amorphous regions of a miscible polycarbonate/polyester blend (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 1237-1247 
    Details
    ISSN: 0887-6266
    Keywords: Polycarbonate ; ThermX ; semicrystalline polyester ; positron lifetimes ; miscible blends ; free volume ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Homopolymers and blends of polycarbonate/ThermX have been investigated by differential scanning calorimetry, dynamic mechanical analysis, density measurements, and positron annihilation lifetime spectroscopy. The study focuses on the chain mobility and free volume in the amorphous miscible regions of the blends and how this mobility and free volume are affected by increasing crystallinity. It is proposed that judicious annealing, which results in increasing crystallinity (while avoiding ageing or transesterification), induces a constraint on the amorphous region leading to an increase in Tg and coalescence of free volume sites. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320711
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular mobility of substituted poly(p-phenylenes) characterized by a range of polymer relaxation techniques (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 1465-1481 
    Details
    ISSN: 0887-6266
    Keywords: poly(phenylene) ; dielectric ; dynamic mechanical ; relaxation ; free volume ; positron annihilation ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The free volume and related mobility properties of substituted poly(p-phenylene) polymers are examined. The techniques used range from positron annihilation, dielectric relaxation, and dynamic mechanical spectroscopy to thermally stimulated currents. Fractional free volume is determined for the samples with different substituted side groups and related to the glass transition temperature. Bulkier groups lead to a greater fractional free volume and lower glass transition temperatures. Comparison of molecular relaxation times using the different characterization techniques demonstrates that there is strong coupling between motion of the main chain and the side groups, on which the dipoles reside. Intermolecular coupling between the main chains at the primary relaxation is shown in this work to be related to the nature of the side chains and resultant free volume, as are the temperature locations of local, secondary relaxations. A qualitative model describing the effect of regiochemistry on the motions and packing of these materials is also proposed. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1465-1481, 1998
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    On the analysis of positron annihilation lifetime spectroscopy data in semicrystalline miscible polymer blend systems (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1191-1202 
    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 free volume probing technique, positron annihilation lifetime spectroscopy (PALS) is used to characterize miscible blends of amorphous polycarbonate with a semicrystalline copolyester at room temperature. The paper describes the analysis required to use the PALS technique to probe the amorphous regions in which the miscibility of the blends occurs. Analysis of the raw PALS data in this system involves taking account of the influence of crystallinity on the PALS results. The results demonstrate that the PALS technique is able to discriminate between free volume in the amorphous regions of as-molded and annealed samples. This difference in free volume between samples of differing thermal history is assigned to the influence of polymer crystals on the stress state of the miscible amorphous regions. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520903
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Compatibilized linear low-density polyethylene/isotactic polypropylene blends studied by positron annihilation lifetime spectroscopy (1995)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 28-33 
    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: Positron annihilation lifetime spectroscopy (PALS), capable of probing free volume, is used to study the effect of compatibilizer concentration, compatibilizer type, and the effect of blend processing on the morphology and properties of an immiscible linear low-density polyethylene/polypropylene system. It is proposed that improvement of fracture toughness due to compatibilization can be attributed to the packing (and bonding) at interfaces. Improved interfacial packing and bonding result in lower free volume concentration than expected from component additivity, with a concomitant increase in plastic deformation on impact.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760350105
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Molecular dynamics in a miscible polyester blend (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 2419-2431 
    Details
    ISSN: 0887-6266
    Keywords: dielectric relaxation ; thermoplastic blend ; coupling ; miscible blend ; polyester ; polycarbonate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic mechanical and dielectric spectra of a miscible polyester and polycarbonate blend are investigated with emphasis on the latter technique. It was found that relaxation spectra for the blends from both techniques are broader than those of the constituent homopolymers. This is ascribed to greater intermolecular coupling and concentration fluctuations within the blends. The composition at which the greatest coupling occurs is dependent on the relaxation technique used and is skewed towards the component which shows the highest degree of intermolecular coupling. A number of parameters, such as relaxation time of the polymer molecules in the blend and relaxation strength, are compared as a function of reduced temperature (experimental temperature scaled by the glass transition temperature). Whereas blend behavior is generally intermediate between that of the homopolymers, it appears as though mobility of compositions with low polyester content have a greater relaxation time and possess a higher activation energy when compared to a simple, weighted average of the corresponding homopolymer values. © 1996 John Wiley & Sons, Inc.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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