Anyone handling powders understands flow properties can easily change when a material is moved from one environment to another. Environmental conditions during processing, handling, or transport including temperature, humidity, electrostatic charge, and time can critically affect flow. For these reasons, multiple testing conditions should be used to analyze the way a powder will flow in a given processing environment.

Comprehensive powder flowability testing can identify how a material may respond to conditions encountered during manufacturing, storage, transport, and handling. As an experienced powder characterization lab, PTL evaluates relevant material behaviors under carefully selected test conditions to generate data that reflect specific processing concerns. These insights can help clients compare formulations, investigate handling challenges, optimize processes, and evaluate material consistency. Selecting appropriate testing methodologies is especially important when properties, such as consolidation, aeration, temperature, or moisture, may influence powder flowability behavior and processing performance.

The FT4 Powder Rheometer by Freeman Technologies is a powder tester which can measure dynamic, bulk, and shear properties in addition to wall friction measurements. The variety of testing techniques allows for the measurement of a powder in several different powder “states”: dynamic, static, or under a stressed condition.

The device measures the energy needed to create specific flow conditions by passing a blade through a conditioned powder sample under various testing methodologies. Since Powder Flowability can be dramatically influenced by entraining air during transfer or by compacting the sample into a container, the FT4 testing methodology incorporates techniques to evaluate as well as limit these conditions. In addition, the procedures reduce handling variability contributed by the operator. The result…improved repeatability and accuracy of data.

Among the results provided are the powder’s flow characteristics in three different packing situations: aerated, conditioned, and consolidated. In this manner, thorough insight is provided regarding flow in differing processing environments. Specific testing includes: stability (repeatability of the flow energy with the same blade speed), variable flow rate (flow energy changes with decreasing blade speed), aeration/de-aeration (how does flow energy change with changes in air velocity through the powder bed?), compaction (comparison between tapping and direct pressure consolidation), permeability (how readily does air pass through the powder?), and compressibility (how does the bulk density change as downward compaction force is applied?).

Another instrument available at PTL for powder flowability is the Anton Paar MCR 302e. This instrument excels at performing shear cell tests. The unique feature of this powder flow measuring instrument is its ability to test powders under elevated controlled temperatures. The measurement area can be enclosed in an oven so the sample can be heated and held at a specified temperature and time during powder flow testing.

Temperature either during the manufacturing and/or storage of a powder can influence flow behavior depending on the material’s physical properties. Properties such as the glass transition temperature, melting point, moisture content, and others are related to temperature. Controlling this parameter during testing with the Anton Paar MCR 302e can more closely mimic processing conditions and differences in the flow properties relative to temperature.

Shear cell testing consists of evaluating how a powder will flow under a consolidated or stressed state. Process engineers use the information from shear cell testing for hopper design or comparison between materials and manufacturing sites; for example, production facilities in different climate zones, if the powder is sensitive to temperature during manufacturing, storage, and processing.

Another test that helps process engineers and powder-handling equipment vendors is wall friction testing. This test can also be performed within the Anton Paar MCR 302e Rheometer’s controlled temperature oven to evaluate if temperature changes the powder’s wall friction behavior. If the powder has a low glass transition temperature, for example, even slightly elevated temperature may cause the material to soften and become sticky within powder handling equipment resulting in processing issues.

The versatility of PTL’s powder flowability instruments has proven beneficial to clients in the pharmaceutical, automotive, cement, food, cosmetic, and industrial sectors. Contact us today to discuss how our powder flow testing capabilities may help answer your powder handling questions.