Abstract SYMPHOS 2011

20
RHEOLOGICAL PROPERTIES OF CONCENTRATED SUSPENSIONS OF
COLLOIDAL AND NON COLLOIDAL PARTICLES
Materials & new products KN8
Pierre J. Carreau
Center for Applied Research on Polymers and Composites (CREPEC), Dept. of
Chemical Eng.,
Ecole Polytechnique, Montreal, QC H3C 3A7, CANADA
Although considerable efforts have been devoted to the determination of the rheological properties of concentrated
suspensions, the behavior of concentrated suspensions is still far from being understood. A new approach has been
developed with the help of the newest generation of high precision rheometers. Instead of the traditional shear
rate sweep method, that is quite disruptive or even destructive for the particle arrangement in the suspension,
softer measurement strategies have been used for understanding phenomena and interactions in concentrated
suspensions. These strategies include low stress creep tests and low strain oscillatory measurement. Also, special
care must be taken in sample preparation and conditioning before doing any rheological measurement. These
strategies have been tested on model suspensions of non colloidal particles (hollow glass beads in low molecular
weight polybutene) and are shown to provide a better understanding of the rheological behavior of concentrated
suspensions.
More recently, we have examined the rheological properties of colloidal suspensions. These include concentrated
suspensions of charged latex particles of poly(styrene-butadiene) and silica particles. The suspensions were found
to behave as elastic solids at small strains and to require a finite stress to flow. This was related to an ordered
structure of the suspensions at rest, resulting from electrostatic and dispersion forces. Important shear-thinning
effects were also observed as a consequence of structure rearrangements under shear. At a fixed shear rate, the
steady-shear viscosity as a function of the ionic strength exhibits a minimum. Under oscillatory shear flow, the
behavior of the concentrated suspensions was found to be non-linear at very small strain amplitude values. The
behavior of these suspensions could be qualitatively described using a structural model.
HIGH VALUE PHOSPHATE MATERIAL DEVELOPMENT,
A SCIENTIST VIEWPOINT.
Materials & new products KN9
Gilles Le Flem
Institut de Chimie de la Matière Condensée de Bordeaux
(ICMCB), CNRS UPR 9048
Avenue du Dr. Schweitzer 33608 PESSAC (FRANCE)
High value material including phosphates can result from: (I) major efforts to maintain and possible improve the
quality of education, (II) cross disciplinary approach (Chemistry, Physics, Geology, Biology etc.), (III) implementation
of new concepts which are able to push back the technological frontiers.
Composite materials, metamaterials (properties depending on the structure and architecture rather than
composition), laser processing, size of the particles (aggregates, nano, micro etc.), chemical reaction in
supercritical atmosphere, surface–functional material, “lab on chip” (microfluidic, micromachining),
template effect ( pre-organization of the final architecture of the material) are typical examples of such new
concepts which have been recently developed.
A non exhaustive list of typical high value phosphate materials resulting from cross-disciplinary approach and new