![]() The most common deviation is shear thinning behavior, where the viscosity of the system decreases as the shear rate is increased. There are two types of deviation from Newton's law that are observed in real systems. The opposite of a dilatant material is a pseudoplastic. Rheopecty is a similar property in which viscosity increases with cumulative stress or agitation over time. Sand that is completely soaked with water also behaves as a dilatant material - this is the reason why when walking on wet sand, a dry area appears directly underfoot. This can readily be seen with a mixture of cornstarch and water (sometimes called oobleck), which acts in counterintuitive ways when struck or thrown against a surface. A large portion of the properties of these systems are due to the surface chemistry of particles in dispersion, known as colloids. Shear thickening behavior occurs when a colloidal suspension transitions from a stable state to a state of flocculation. The properties of these suspensions depend on Hamaker theory and Van der Waals forces and can be stabilized electrostatically or sterically. This behavior is only one type of deviation from Newton's law of viscosity, and it is controlled by such factors as particle size, shape, and distribution. This behaviour is usually not observed in pure materials, but can occur in suspensions.Ī dilatant is a non-Newtonian fluid where the shear viscosity increases with applied shear stress. Such a shear thickening fluid, also known by the initialism STF, is an example of a non-Newtonian fluid. Not to be confused with Dilatancy (granular material).Ī dilatant ( / d aɪ ˈ l eɪ t ə n t/, / d ɪ-/) (also termed shear thickening) material is one in which viscosity increases with the rate of shear strain.
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