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Stability and Microrheology analysers |
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Turbiscan™:
the reference for stability analysis
Physical stability and shelf life are key parameters in the development of concentrated liquid dispersions.
TURBISCAN™: THE CONCEPT
Turbiscan™ technology consists in measuring the Backscattering and Transmission intensities versus the sample height in order to detect particle size change (coalescence, flocculation) and phase separation (sedimentation, creaming)
STABLE
UNSTABLE: SIZE CHANGE
UNSTABLE: PHASE SEPARATION
Microrheology:
a new domain of Rheology
To study viscoelastic behaviour at rest.
THERE ARE 2 CLASSES OF MICRORHEOLOGY
Active microrheology:
An external driving force is applied locally to the probe particle(s)
(magnetic or electric fields, optical tweezer, …) and the resultant
displacements is measured.
Passive microrheology:
No external stress is applied (measurement at rest). The local force
acting on the particle is due to thermal energy (Brownian Motion) and
the response is measured by probing the time-dependent Mean Square Displacement of the particle (MSD).
For instance, the displacement of the
particles in a purely viscous fluid grows linearly in time, whereas in
an elastic fluid the particles are limited in their displacement.
MSD IS THE MASTER CURVE TO ACCESS RHEOLOGICAL PROPERTIES
Using the Generalized Stokes Einstein Relation (GSER), it is possible to calculate from MSD curve:
- The Elastic modulus G’µR versus the frequency
- The viscous modulus G’’µR versus the frequency
Using
Generalized Maxwell model, it is possible to calculate the relaxation
time, the macroscopic viscosity and the plateau elasticity Gp’µR .
These parameters enables to determine microstructure property like the
mesh size.
Passive microrheology has been extensively studied by D. Weitz - Harvard University and T. Mason - UCLA University, et. al in the 1990’s.
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