Fließfähigkeit

Fließfähigkeit is a German term that translates to “flowability” in English. It refers to the ability of a material, particularly a granular or powdered substance, to flow under its own weight or when subjected to shear forces. In industrial and scientific contexts, the assessment of flowability is essential for processes such as mixing, transporting, filling, and handling of bulk solids. Poor flowability can lead to segregation, uneven packing, clumping, and operational inefficiencies, while excellent flowability ensures uniform distribution and ease of handling.

The measurement of flowability typically employs standardized tests such as the flow function tester, the Hall flowmeter, or the angle of repose test. Results are expressed in terms of flow index, angle, or other quantitative metrics. Material properties that influence flowability include particle size distribution, shape, surface roughness, moisture content, and the presence of fines or contaminants. Environmental conditions such as humidity, temperature, and vibration also play a role. For finely divided materials, interparticle forces such as van der Waals attractions, electrostatic charges, or capillary bridges stemming from moisture can significantly hinder flow.

In industries such as pharmaceuticals, food, mining, and construction, controlling flowability is critical for product quality and process reliability. Techniques to improve flowability include adding flow aids (e.g., talc, magnesium stearate, or PTFE powders), adjusting particle size distribution, modifying moisture levels, or mechanically agitating the material. Understanding the flowability of a material enables engineers to design equipment, optimize processes, and predict behavior under varying operational conditions.