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Christian Clasen
International Workshop on Rheology and Structural Design of Complex Fluids 2011

Appl. Rheol. 21:3 (2011) 185-185

Cite this publication as follows:
Clasen C: International Workshop on Rheology and Structural Design of Complex Fluids 2011, Appl. Rheol. 21 (2011) 185.

Christian Clasen, H. Pirouz Kavehpour, Gareth H. McKinley
Bridging Tribology and Microrheology of Thin Films

Appl. Rheol. 20:4 (2010) 45049 (13 pages)

An enhanced version of the flexure-based microgap rheometer (FMR) is described which enables rheological measurements in steady state shearing flows of bulk fluid samples of PDMS with an absolute gap separation between the shearing surfaces of 100 nm - 100 μmm. Alignment of the shearing surfaces to a parallelism better then 10-7 rad allows us to reliably measure shear stresses at shear rates up to 104 s-1. At low rates and for shearing gaps < 5 mm the stress response is dominated by sliding friction between the surfaces that is independent of the viscosity of the fluid and only determined by the residual particulate phase (dust particles) in the fluid.This behaviour is similar to the boundary lubrication regime in tribology.The absolute gap control of the FMR allows us to systematically investigate the flow behaviour at low degrees of confinement (gap separations 100 nm - 2 μm) that cannot be accessed with conventional (controlled normal load) tribological test protocols.

Cite this publication as follows:
Clasen C, Kavehpour HP, McKinley GH: Bridging Tribology and Microrheology of Thin Films, Appl. Rheol. 20 (2010) 45049.

J.P. Plog, W.-M. Kulicke, C. Clasen
Influence of the Molar Mass Distribution on the Elongational Behaviour of Polymer Solutions in Capillary Breakup

Appl. Rheol. 15:1 (2005) 28-37

Commercially available, blended methylhydroxyethyl celluloses with similar weight-average molar masses but varying molar mass distributions were characterized by different techniques like steady shear flow and uniaxial elongation in capillary breakup experiments. The determined relaxation times t were then correlated with the absolute molar mass distribution acquired via SEC/MALLS/DRI (combined methods of size-exclusion-chromatography, multi angle laser light scattering and differential refractometer). In order to describe the longest relaxation time of the polymers in uniaxial elongation via integral mean values of the molar mass distribution, defined blends of polystyrene standards with varying molar mass distributions were characterized. The obtained data was scaled via different moments of the molecular weight distribution and could be correlated with the results obtained for the methylhydroxyethyl celluloses.

Cite this publication as follows:
Plog JP, Kulicke W-M, Clasen C: Influence of the Molar Mass Distribution on the Elongational Behaviour of Polymer Solutions in Capillary Breakup, Appl. Rheol. 15 (2005) 28.


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