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  • 1
    Electronic Resource
    Electronic Resource
    Thermal conductivity in ultraoriented polyethylene (1992)
    s.l. : American Chemical Society
    Macromolecules 25 (1992), S. 3500-3502 
    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/ma00039a030
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  • 2
    Electronic Resource
    Electronic Resource
    High thermal conductivity of polymers: Possibility or dream? (1996)
    Springer
    Journal of computer-aided materials design 3 (1996), S. 273-280 
    Details
    ISSN: 1573-4900
    Keywords: Thermal conductivity ; Polymers ; Orientation ; Phonon focussing ; Boundary resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary Using the simple kinetic formula of thermal conductivity, it is shown that the mean free path is the limiting factor of thermal conductivity. Standard arguments on phonon-phonon interaction lead to realize that isotropic polymers cannot exceed thermal conductivities k ∼ 1 W/mK. Orientation of polymers gives a strong enhancement of k in orientation direction, due to the effect of phonon focussing. For the simplest chain, the polyethylene molecule, up to 37 W/mK have been measured. Possible values of 70 W/mK can be extrapolated for material with the modulus of the chain. Even higher values can be envisaged for perfect crystalline material. The integration of such a material must take care of minimizing the boundary resistance to the adjacent solid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01185664
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal conductivity ofn-Tetracosan around the liquid-liquid transition temperatureT u (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 603-606 
    Details
    ISSN: 1435-1536
    Keywords: n-Tetracosan ; thermal conductivity ; transient hot strip ; liquid-liquid 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 Forn-Tetracosan the temperature dependence of the thermal conductivity has been determined between 52 °C and 150 °C by the transient hot strip method. A decreasing thermal conductivity is followed by a constant one forT≳100 °C. The change in slope can be well estimated by using data of Brillouin scattering and specific volume measurements thus confirming the existence of theT u -phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01421896
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  • 4
    Electronic Resource
    Electronic Resource
    Are there two temperature regions with different structure of N-alkane melts? (1980)
    Springer
    Polymer bulletin 2 (1980), S. 663-669 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary From the comparison of measurements of viscosity, Brillouin scattering and depolarized Rayleigh scattering it appears that two types of structure exist in the n-alkane melts. The regions where these structures are dominant are separated by a relatively well defined temperature Tu. The difference in the activation energies of viscous flow in these two regions is ΔE= 2.8 kJ/mol. From the molecular weight dependence of Tu we conclude that polyethylene always retains the low temperature structure which should not be much different from that of n-alkanes with n≳28.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254450
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  • 5
    Electronic Resource
    Electronic Resource
    Brillouin spectroscopy at the melt transition of poly-4-methyl-pentene-1: Discontinuous melting of superstructures? (1981)
    Springer
    Polymer bulletin 4 (1981), S. 591-596 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The elastic properties of Poly-4-methylpentene-1 around the melt transition have been studied by Brillouin spectroscopy. A discontinuous change of the sound velocity is observed in the melting region of 10 K indicating a rather discontinuous melting and formation of spherulites with sharp boundaries. Another result is that practically the final elastic properties of the spherulites appear already during their formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256286
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  • 6
    Electronic Resource
    Electronic Resource
    The role of phonon focussing and structure scattering in oriented semicrystalline polymers (1989)
    Springer
    The European physical journal 77 (1989), S. 219-228 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements of anisotropic thermal diffusivity and of the velocity of hypersound have been performed at room temperature on one set of stretched low density polyethylene (crystallinityv c =0.4). The elastic anisotropy increases with the stretching ratio λ as does the heat conduction anisotropy. It is argued that the heat conduction cannot be traced back to properties of extended crystalline and amorphous phases. The reason for the latter is the smallness of the microphases giving rise only to non-propagating modes. Phonon focussing of superstructure phonons together with the wavelength dependence of their scattering can explain the observed effects. From the parameters found and from a semiquantitative description of the temperature dependence down to 4 K it is concluded that the main transport could be due to hopping mechanisms where the localized phonons may be fractons. It is conjectured that the energy flow is assisted or triggered by the long wave length phonons via anharmonic coupling giving rise to the dependence on direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01313666
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  • 7
    Electronic Resource
    Electronic Resource
    Heat conduction in highly oriented polyethylene (1994)
    Springer
    The European physical journal 94 (1994), S. 461-468 
    Details
    ISSN: 1434-6036
    Keywords: 66.70 ; 65.40 ; 44.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The variety of structures found in polymers makes it impossible to thoroughly understand all the mechanisms affecting heat conduction. With the example of polyethylene it is shown that highly oriented polymers can be treated as strong anisotropic continua in the defect scattering limit. Using direction dependent sound velocities from Brillouin scattering we find elastic contributions to be dominated by the angular dependence of the phonon density. The direction dependence of the specific heat contributions is accounted for by using the Debye formalism inq-space. The cut off wave vector is determined by fitting the low temperature specific heat. The resulting relaxation lengths turn out to be largely temperature independent in agreement with the assumption of predominant structure scattering. At 8 K〈T〈40 K a minimum in the relaxation length parallel to the chain molecules indicates resonance scattering by local modes. They have been identified as the so called longitudinal acoustic eigenmodes (LA-modes) of the very small crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01317408
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  • 8
    Electronic Resource
    Electronic Resource
    About the transition of n-alkanes above the melting point comment to the paper by P. Claudy and J.M. Létoffé (1983)
    Springer
    Polymer bulletin 9 (1983), S. 252-253 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00283716
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  • 9
    Electronic Resource
    Electronic Resource
    The elastic properties of C36H74 single crystals from Brillouin-spectroscopy (1980)
    Springer
    Polymer bulletin 3 (1980), S. 633-640 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The elastic properties of C36H74 single crystals have been investigated at room temperature by Brillouinspectroscopy. A nearly complete set of data is presented for the crystallographic (a,b)-plane. Furthermore the longitudinal sound velocity normal to that plane could be determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00285299
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  • 10
    Electronic Resource
    Electronic Resource
    Structure and anisotropy in polycarbonate III. Study of elastic and optical properties of oriented samples with the method of high resolution Brillouin spectroscopy (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 761-773 
    Details
    ISSN: 1435-1536
    Keywords: Polycarbonate ; oriented polymers ; elastic and optical anisotropy ; Brillouin spectroscopy ; aggregate model ; orientation parameters
    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 High resolution Brillouin spectroscopy (BS) has been used to investigate elastic and optical properties of uniaxially drawn samples of polycarbonate (PC). The results are discussed in the framework of the single phase aggregate model (SPAM) of Ward. According to a recently developed evaluation technique, the SPAM parameters of PC are determined, resulting in the following elastic constants of the structural units:c 33 0 =33 GPa,c 11 0 =7 GPa,c 13 0 =9.7 GPa,c 44 0 =1.4 GPa, andc 66 0 =1 GPa. A nearly quadratic dependence of the orientation parameterP 4 onP 3 results, which can be explained by a modified pseudoaffine deformation scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418451
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