1.2 Pseudo plastic and Dilatant Physiognomies
Pseudo plasticity is a phenomenon displayed by drilling mud systems where the viscosity of the fluid decreases with an increase in shear rate. This is also known as shear thinning. The reverse case of the viscosity of the fluid increasing with an increase in the shear rate is termed dilatant also known as shear thickening. It is affected by properties such as particle size, shape and dissemination all of which are controlled by the Hamaker theory and Van der Waals forces.