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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Rheodielectric spectroscopy on heterogeneous polymer systems —electrorheological fluids (1995)
    Springer
    Colloid & polymer science 273 (1995), S. 848-856 
    Details
    ISSN: 1435-1536
    Keywords: Electrorheological fluids ; dielectric spectroscopy ; colloidal suspensions
    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 technique of rheodielectric spectroscopy is used to investigate the dielectric behaviour of electrorheological fluids (ERF) as a function of external electrical DC-field and/or shear rate. Commercial ERF's consisting of mesoscopic polyurethane particles in a silicone oil matrix were studied. The particles contain a salt which leads to strong dipole moments via the Maxwell-Wagner-Polarization (MWP) if subjected to an external electrical field. In an electrical field the dipoles and, concomittantly, the particles motion become correlated leading to the formation of solid-like structures and significant changes in the viscosity. We demonstrate that dielectric spectroscopy is capable of monitoring the field and shear rate effects in terms of relaxation strength and relaxation time of the MWP. In electrical or shear fields dipole-dipole correlations increase the MWP's relaxation strength, so that we are able to observe structure formation with dielectric spectroscopy, especially the time resolved response of the ERF to changes in the electrical field or the shear rate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657634
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  • 3
    Electronic Resource
    Electronic Resource
    On the static scattering of linear and cyclic copolymers in solution (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 1629-1636 
    Details
    ISSN: 0887-6266
    Keywords: linear copolymer ; cyclic copolymer ; static scattering ; effects of temperature ; concentration and scattering angle ; apparent virial coefficient ; apparent radius of gyration ; RPA ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In this article, the static scattering properties of linear and cyclic copolymers in solution are discussed. A theoretical formalism is proposed which could be useful in examining the recent light scattering data obtained by Amis et al. The cases of a triblock linear copolymer made of three equal blocks PDMS-PS-PDMS in cyclohexane, and its counterpart, the cyclic diblock PDMS-PS in the same conditions of molecular weight, composition, concentration, and temperature are considered. Another linear copolymer made of two blocks of the same nature as the cyclic copolymer is also investigated within the same formalism. The variations of the scattered intensity with the wave vector q, the concentration of polymer and the temperature of the solution are considered. The effects of temperature on the apparent virial coefficient and the effects of concentration on the apparent radius of gyration are also discussed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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