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Miroslav Mrlik, Vladimir Pavlinek, Petr Saha, Otakar Quadrat
Electrorheological properties of suspensions of polypyrrole coated titanate nanorods

Appl. Rheol. 21:5 (2011) 52365 (7 pages)

The behaviour of silicone-oil suspensions of titanate nanorods coated with polypyrrole base in electric field has been investigated. Unlike suspension of globular particles of neat polypyrrole, rod-like particles show a stronger electrorheological (ER) effect corresponding to high rigidity of the structure. A great influence of the oil viscosity on the ER efficiency was observed. A good reproducibility of the effect and a fast response to the switching-on and -off the electric field has been confirmed by monitoring the time course of shear stress under controlled shear rate.

Cite this publication as follows:
Mrlik M, Pavlinek V, Saha P, Quadrat O: Electrorheological properties of suspensions of polypyrrole coated titanate nanorods, Appl. Rheol. 21 (2011) 52365.

Martin Stenicka, Vladimir Pavlinek, Petr Saha, Natalia V Blinova, Jaroslav Stejskal, Otakar Quadrat
Electrorheology of suspensions of variously protonated polyaniline particles under steady and oscillatory shear

Appl. Rheol. 20:5 (2010) 55371 (7 pages)


Electrorheological (ER) and dielectric properties of silicone-oil suspensions of polyaniline (PANI) particles protonated with phosphoric and tetrafluoroboric acids to various doping level have been investigated. The particle conductivity was thus varied between the order of 10-9 S/cm and 10-4 S/cm. The dynamic yield stresses obtained at controlled shear rate mode viscometry, the storage moduli from the oscillatory shear experiments and the dielectric relaxation times from frequency dependences of dielectric constant and loss factor were used as criteria of rigidity or elasticity of ER structures and particle mobility in the electric field. The conductivity of suspension particles plays a decisive role in their ER behaviour. The ER efficiency increased as conductivity of dispersed particles raised, irrespective of the type of employed acid used for the protonation of PANI.

Cite this publication as follows:
Stenicka M, Pavlinek V, Saha P, Blinova NV, Stejskal J, Quadrat O: Electrorheology of suspensions of variously protonated polyaniline particles under steady and oscillatory shear, Appl. Rheol. 20 (2010) 55371.

V. Pavlinek, P. Saha, K. Perez-Gonzalez, L. de Vargas, J. Stejskal, O. Quadrat
Analysis of the Yielding Behavior of Electrorheological Suspensions by Controlled Shear Stress Experiments

Appl. Rheol. 16:1 (2006) 14-18

The yielding behavior of two model electrorheological suspensions of uncoated silica particles and silica coated with polyaniline base in silicone oil using controlled shear rate and controlled shear stress experiments has been analyzed. The results demonstrate that unlike the uncertain dynamic yield stress values estimated from the results obtained in the former mode by extrapolation of the unsteady shear stresses to zero shear rate, the controlled shear stress measurement permits to detect sensitively the region starting from the initial rupture of particle chain structure in the electric field at rest corresponding to a static yield stress and ending in total breakage of suspension structure at a breaking stress. The latter quantity can be detected with a good accuracy and proved to be a reliable criterion of the stiffness of electrorheological (ER) structure.

Cite this publication as follows:
Pavlinek V, Saha P, Perez-Gonzalez J, DeVargas L, Stejskal J, Quadrat O: Analysis of the Yielding Behavior of Electrorheological Suspensions by Controlled Shear Stress Experiments, Appl. Rheol. 16 (2006) 14.


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