Rheologische

Rheologie is the science that studies the deformation and flow of matter. The adjective rheologische denotes anything related to rheology. The field covers liquids, suspensions, gels, pastes, polymers and foams, and examines how materials respond to applied stresses or strains over time and under different temperatures and shear conditions. The term rheology derives from Greek rheo- 'flow' and logos 'study'.

Key concepts include viscosity, viscoelasticity and yield behavior, along with time-dependent phenomena such as thixotropy. Viscosity measures resistance to shear flow; Newtonian liquids have constant viscosity, while non-Newtonian materials change viscosity with shear rate. Viscoelasticity materials show both elastic (solid-like) and viscous (liquid-like) responses, often described by storage modulus G' and loss modulus G'' in oscillatory tests. Yield stress marks the transition from a solid-like to flowing state.

Measurement methods include rheometry, using rotational rheometers to obtain flow curves and to perform oscillatory tests, capillary rheometers for high-shear conditions, and specialized techniques for micro- and nano-rheology. Tests quantify how viscosity, G', G'', and other parameters depend on frequency, temperature, and time, enabling comparative material characterization.

Applications span polymers, foods, cosmetics, pharmaceuticals, cement and asphalt, among others. Rheological data support material design, process optimization, quality control and predictive modeling of processing operations such as mixing, pumping, extrusion and storage. In German-language literature, rheologische Eigenschaften describe the rheological properties of materials.