Rheology of Suspensions, Dispersions, or Emulsions

The rheology 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.

Rheology based measurements can help predict which formulations might exhibit flocculation, coagulation or coalescence, resulting in undesired effects such as settling, creaming, separation, etc. Some common rheology measurements and parameters include:

• 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 rheology products:

	Bohlin Gemini HR nano and Bohlin Gemini An advanced range of modular and compact rheometers with 'fluids to solids' capability. They are optimized for both strain controlled and stress controlled rheology measurements, can accept an extensive range of temperature control options, and have wide application in research and product development rheology.
	Bohlin C-VOR A high resolution, modular rheometer system with triple-mode control which allows strain, stress or shear rate controlled rheology measurements to be performed using a single test station.
	Bohlin CVO A flexible rheometer system suitable for research, product development, and quality control rheology measurements.
	Bohlin V88 An easy to use viscometer which provides accurate viscosity measurements at single or multiple shear rates.
	Rosand RH7/10-D Advanced, powerful floor standing capillary rheometry units suitable for research and product development rheology.
	Rosand RH2000 Bench-top, capillary rheometers suitable for rheology measurements for research, product development, and quality control.