Frittflytende

Frittflytende, or free-flowing, describes powders and granular materials that readily flow under gravity with little cohesion. The term is commonly used in engineering, pharmaceuticals, food processing, and materials handling to distinguish such materials from cohesive powders that tend to arch, bridge, or clump together. Free-flowing behavior facilitates dosing, filling, sieving, conveying, and bulk handling.

Flowability is often assessed with simple and standardized tests. The angle of repose measures how steep a pile of powder can be before it collapses, indicating cohesion. Flow through a funnel or-orifice tests, such as the Hall flow, provide practical flow rates. Other indicators include the Hausner ratio and Carr index, derived from bulk and tapped density, which reflect compressibility and inter-particle friction. Humidity and electrostatic effects can alter measurements and real-world performance.

Factors influencing frittflytende behavior include particle size distribution, shape, and surface roughness; moisture content; presence of fines or agglomerates; and cohesive inter-particle forces such as van der Waals attraction. Materials with spherical or near-spherical particles and low moisture tend to flow better, while very fine, irregular, or moist powders often exhibit poor flow.

Methods to improve flow include granulation or agglomeration to create larger, more uniform particles; thorough drying and control of humidity; addition of glidants or anti-caking agents; coating particles to reduce cohesive contacts; and optimizing process equipment and hopper design to minimize arching and rat-holing.

Contextual examples include pharmaceutical powders for tablet manufacturing, dry food ingredients like flour and sugar, cement and mineral powders in construction, and agricultural granules. The suitability of a material as frittflytende depends on its intended handling and processing conditions.

Etymology: from Norwegian, combining fritt (freely) and flytende (flowing).