ickenewtonska

ickeNewtonska refers to materials or fluids that do not obey Newton's law of viscosity, meaning their viscosity changes with the rate of deformation or over time. In Newtonian fluids, shear stress is proportional to shear rate, yielding a constant viscosity. In ickeNewtonska materials, the relationship between stress and shear rate is nonlinear, and the effective viscosity can vary as the applied force or duration of stress changes.

Common categories include shear-thinning (pseudoplastic) fluids, where viscosity decreases with increasing shear rate; shear-thickening (dilatant) fluids, where viscosity rises with higher shear rate; and yield-stress fluids, such as Bingham plastics, which behave as solids until a threshold stress is exceeded. Time-dependent behaviors include thixotropic fluids, whose viscosity decreases under constant shear and gradually recovers when at rest, and rheopectic fluids, which become more viscous over time under shear.

Examples frequently cited are ketchup and many sauces (shear-thinning), a cornstarch–water mixture often called oobleck (shear-thickening under impact), toothpaste (yield stress), and certain paints and clays (thixotropic or viscoelastic behavior). Mechanistically, non-Newtonian behavior arises from microstructural changes in the fluid, such as rearrangements of polymers, the formation or breakage of particle networks, or phase changes under stress.

Applications span food processing, cosmetics, pharmaceuticals, oil drilling fluids, paints and coatings, 3D printing, and construction materials. The term ickeNewtonska is used in some Swedish-language literature to denote non-Newtonian behavior; it is generally interchangeable with non-Newtonian, though not tied to a single formal framework. See also non-Newtonian fluid and rheology.