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  • Structure  (1)
  • light transmission  (1)
  • morphology  (1)
  • Springer  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Reversible morphological changes in poly (ether ester) thermorplastic elastomers during deformation as revealed by small-angle x-ray scattering (1993)
    Springer
    Colloid & polymer science 271 (1993), S. 811-823 
    Details
    ISSN: 1435-1536
    Keywords: Thermoplastic elastomers ; SAXS ; deformation ; morphology
    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 scattering behavior of undrawn and drawn annealed bristles of thermoplastic elastomers with conventional and higher molecular weight based on poly (butylene terephthalate) as hard segments and poly (ethylene glycol) as soft segments in a ratio of 49/51 wt.% is studied. Small-angle x-ray scattering (SAXS) measurements with an area detector are carried out on single bristies under or without applied stress and with deformations up to 300%. At low macrodeformations (ε≤30–40%) the morphology of the predrawn samples represents assemblies of parallel crystalline lamellae positioned perpendicular to the stretching direction. These morphological characteristics remain unchanged within the entire deformation range (up to ε=300%) for the predrawn samples of lower molecular weight. For the initially undrawn sample of larger molecular weight reversible orientation and disorientation of the crystallites (microdomains) is established in the same deformation range. Common morphological features are found for the predrawn and undrawn samples with increased molecular weight at medium (ε=50–150%) and high (ε=150–300%) deformation ranges. For both samples in an unloaded relaxed state the x-ray patterns can be explained by a zig-zag arrangement of crystalline lamellae, i.e., the microdomains are inclined to the stretching direction. After loading, the microdomains transform to a position perpendicular to the stretching direction. This observed morphological transition is found to be reversible and becomes more pronounced with progressing deformation. It is suspected to contribute to reversible macrodeformations of thermoplastic elastomers in many cases and may be related to the large amount of tie-molecules created during solid-state reactions in those materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00652763
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  • 2
    Electronic Resource
    Electronic Resource
    Field-induced structural ordering in electrorheological fluids (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 1156-1162 
    Details
    ISSN: 1435-1536
    Keywords: Electrorheological fluids ; colloids ; rheodielectric spectroscopy ; light transmission
    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 Structural relaxations of an electrorheological fluid (ERF) due to changes in the applied electrical field strength or shear rate are observed on time scales 1 s〈t〈40 000 s. Commercial ERFs consisting of mesoscopic polyurethane particles in a silicone oil matrix were studied by three different experimental techniques in order to obtain and compare the characteristic relaxation times. It is demonstrated that dielectric spectroscopy, viscosimetry and light transmission experiments represent the same results concerning the structural relaxation phenomena of ERFs when electrical fields are applied. The tendency of strong induced dipoles to align the particles in the direction of the field increases the effective dipole moment and therefore Δε, the shear viscosity ν and the amount of light transmitted along the field direction in an ITO/glass sandwich cell. The optical experiment is capable of resolving fast processes within the first 1 ms if large electrical fields are applied. The effects of electrophoresis and shearing, which both counteract the field induced structures, are also addressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653084
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of molecular weight on the structure and temperature behavior of a thermotropic main-chain liquid crystalline copolyester (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 23-31 
    Details
    ISSN: 1435-1536
    Keywords: Structure ; phase transitions ; x-ray scattering
    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 structure of a fully aromatic thermotropic liquid crystalline (LC) copolyester poly-[(phenyl-p-phenylene)-co-(terephthalate)-co-(p-hydroxybenzoate)] (PES) prepared from terephthalic acid, phenylhydroquinone, andp-hydroxybenzoic acid at a molar ratio of 45/45/10, respectively, was studied at ambient and elevated temperatures by means of x-ray diffraction and differential scanning calorimetry as a function of molecular weight. On heating of PES fibers with fixed ends an irreversible phase separation process takes place above the glass transition point and two different crystalline phases are formed. A model is proposed where the phases are assumed to contain the constituents of the statistical copolymer in different amounts. The relative volume fraction of the two crystalline modifications depends on the molecular weight of the investigated fibers. At higher temperatures the melting of the two crystalline phases and their transition to a LC nematic mesophase is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655670
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