Glossario

Non-Newtonian

A non-Newtonian fluid is one that exhibits a viscosity that varies as a function of the applied shear rate or shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress

Examples of non-Newtonian materials are Shear ThinningThe most common type of non-Newtonian behavior is shear thinning or pseudoplastic flow, where the fluid vis­cosity decreases with increasing shear.shear thinning (pseudoplastic), plastic (exhibiting a yield StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress) and Shear ThickeningWhile most suspensions and polymer structured mate­rials are shear thinning, some materials can also show shear thickening behavior where viscosity increases with increasing shear rate or shear stress.shear thickening (dilatant).

Most formulated materials are non-Newtonian to give beneficial material functionality, such as a high viscosity at rest to promote stability, but then shear thinning to facilitate ease of application. Rheology is the study of this non-Newtonian behaviour which results from the “break down” under shear of the “associated” (micro)structure in the sample.