Measuring suspensions, dispersions or emulsions

The measurement of rheological properties of suspensions, colloidal dispersions and emulsions provide critical information for product and process performance in many industrial applications and in order for them to give proper product performance, or to process efficiently, they must be stable. But these are often complex formulations of solvents (or fluids), suspended particles of varying size and shape, and various additives used to affect stability.

Many factors affect stability, such as: hydrodynamic forces, Brownian motion, strength of interparticle interactions, volume fraction, electrostatic forces, steric repulsion, size and shape of particles, to name a few. Measuring the rheology of a formulation gives an indication of the colloidal state and interactions that are occurring.

Rheological measurements can enable prediction of which formulations might exhibit flocculation, coagulation or coalescence, resulting in undesired effects such as settling, creaming, separation, etc. Some of the common rheological measurements used and parameters measured are as follows:

• Flow behavior of non-Newtonian materials, which helps indicate degree of dispersion and/or flocculation as well as shear thinning or thickening which often helps determine processing behavior.
  
• G’ (storage modulus) and G’’ (loss modulus) as a function of frequency which determines viscoelastic behavior as a function of time (inverse of frequency), and can help determine the degree of stability of a formulation under "at rest” conditions or during transport.
  
• Creep/recovery tests to determine zero shear viscosity or the maximum viscosity of the fluid phase that must be sufficiently high to prevent sedimentation

Available products:

	Bohlin Gemini II
	Bohlin CVO
	Bohlin V88
	Rosand RH7/10-D
	Rosand RH2000