High Shear Mxing
“A high shear mixer disperses, or transports, one phase or ingredient (liquid, solid, gas) into a main continuous phase (liquid), with which it would normally be immiscible. A rotor or impellor, together with a stationary component known as a stator, or an array of rotors and stators, is used either in a tank containing the solution to be mixed, or in a pipe through which the solution passes, to create shear. A high shear mixer can be used to create emulsions, suspensions, lyosols (gas dispersed in liquid) and granular products. It is used in the adhesives, chemical, cosmetic, food pharmaceutical and plastics industries for emulsification, homogenization, particle size reduction and dispersion.” (Wikipedia, High Shear Mixing, 3/14/2011)
Recent Journal Articles
Electrical capacitance tomography as a monitoring tool for high-shear mixing and granulation
(4090-4100) Chemical Engineering Science 66 #18 (2011)
Rimpiläinen et al of the University of Eastern Finland, Finland, used electrical capacitance tomography (ECT) for monitoring high-shear mixing and high-shear granulation. A finite element method (FEM)-based reconstruction algorithm was utilized to take into account the specific geometrical characteristics of the experimental set-up. Two-dimensional ECT tomograms, mixing index curves and permittivity fractions were computed based on the measurements, and their suitability in the analysis of the processes was assessed. It was found that the different mixing processes and the different granulation processes could be analyzed based on these quantities. (RDC 7/12/2011)
Structure and properties of isobutylene-isoprene rubber/swollen organoclay nanocomposites prepared by shear mixing
(225-231) Chinese Journal of Polymer Science 29, #2 (2011)
Tan et al, China, prepared high-performance isobutylene-isoprene rubber/swollen organoclay nanocomposites by shear mixing. Better dispersion of nanoclay layers in rubber matrix developed compared with traditional melt compounding. The nanocomposites also showed significantly improved mechanical properties and gas barrier property. As a mechanism, the molecules of organic swelling agent play a vital role in accelerating the diffusion and intercalation of the matrix molecules. (RDC 2/11/2011)
Phase behavior of polystyrene acrylonitril copolymer and polymethylmethacrylate blends under shear
(310–317)Journal of Polymer Science B: Polymer Physics 49, #4 (2011)
Berrayah and Maschke described the effect of shear on mixing as a sum of two terms, the Flory–Huggins free energy of mixing and the excess free energy stored during flow. In the presence of shear flow, the excess free energy is expressed in terms of the viscosity and the shear modulus. The curvature of the variation of viscosity versus composition has a tremendous impact upon the nature of phase separation. Phase diagrams are described by the spinodal curves and show miscibility enhancement with increasing shear rate. A good correlation is found with experimental data of the literature on blends of polystyrene acrylonitrile copolymer and polymethylmethacrylate. (RDC 1/13/2011)