Berlin 2015 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 45: P10: Colloids and Complex Liquids

CPP 45.9: Poster

Mittwoch, 18. März 2015, 10:00–13:00, Poster A

The influence of Brownian motion on sheared nanocomposites: New experimental results and a revision of Peclet-time as a characteristic time scale — •Rick Dannert, Roland Sanctuary, and Jörg Baller — University of Luxembourg, Laboratory for the Physics of Advanced Materials, Grand-Duchy of Luxembourg

Oscillatory shear tests performed on concentrated and semi-diluted suspensions of spherical silica nanoparticles in Diglycidyl Ether of Bisphenol A (DGEBA) have revealed a low-frequency relaxation process. The latter was interpreted as Brownian stress relaxation resulting from strain-induced perturbations of the isotropic filler distribution [1]. To cover a broader concentration range we have extended the rheological investigation of the low-frequency anomaly to ultra-diluted DGEBA/silica suspensions. We illustrate that the Brownian relaxation process depends in a complex manner on the volume concentration: For very dilute systems, the relaxation frequency increases with the concentration, whereas for semi-dilute or concentrated systems, the opposite behaviour can be observed. This non-monotonic dependency of the relaxation frequency can no longer be modelled by classical Peclet frequencies. Therefore we show that modified Peclet-frequencies including a structural, concentration dependent length scale viz. the mean particle distance lead to an accurate description of the Brownian relaxation process for all concentrations.

R. Dannert, R. Sanctuary, M. Thomassey, P. Elens, J.K. Krüger, J. Baller, Rheologica Acta, 53 (2014) 715-723.