8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P9.57A rheological study (thixotropy) of some filled polymersF. J. Rubio-Hernández 1 and N. M. Páez-Flor 11 University of Málaga, C/ Doctor Ortiz Ramos s/n, 29071, Málaga, SpainCombining equilibrium and non-equilibrium rheological tests, the thixotropic behavior of fourfilled polymers has been studied. Rheological tests were performed with a RS600 rheometer(Haake-Thermo). 1 20 mm cone-plate geometry has been used. Steady flow curves in the shearrate interval considered reveal that each polymer shows shear regions in which different independenttime rheological behaviors can be observed. For example, while Aerosil R816/PEG2000behaves as a shear-thinning fluid in the whole shear rate region, Aerosil R816/PPG400 shows ashear-thickening region located between two shear-thinning regions. Considering thixotropy astime-dependent shear-thinning and antithixotropy as time-dependent shear-thickening, a variety ofnon-equilibrium studies have been made with these systems. Step-down and step-up tests wereperformed to determine the build-up and break-down of the thixotropic structures. The resultswere analyzed with a micro-structural model in which two equations govern the phenomena. Thefirst one is the state equation, and the second one is the kinetic equation. The results have beeninterpreted on basis on particle structure formation and influence of length and shape of polymermolecules.57