The flowability characteristic of a powder is directly related to both the physical properties of the material itself, as well as the specific processing conditions in the handling system. Consequently, for such a complex system, a “single number” used to describe the flow of a powder may not be realistic or may not provide sufficient information. Playing a role in how powders flow are physical properties such as: particle size, size distribution, shape, surface area, and density.
Anyone who handles powders understands that 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. PTL has the capability to evaluate several of these factors for clients material.
The FT4 Powder Rheometer by Freeman Technologies is a universal 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.
This instrument takes a new approach to powder testing. 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 end result…improved repeatability and accuracy of data.
During a typical Powder Flowability Study, the material is tested and the results are reported graphically and numerically. Among the results provided are the powder’s flow characteristics in three different packing states:
In this manner, thorough insight is provided regarding flow in differing processing environments. Specific testing includes:
Stability (How repeatable is the flow energy with the same blade speed?)
Variable Flow Rate (How does the flow energy change with decreased blade speed?)
Aeration & De-aeration (How does the flow energy change with a change in air velocity passed through the powder bed?)
Compaction (What is the comparison between tapping and direct pressure as a mode of consolidation?)
Permeability (How readily does air pass through the powder?)
Compressibility (How does the bulk density change as a downward compaction force is applied?)
In addition to the above typical Powder Flowability Study, the following tests may be useful, for an additional charge. Processing conditions for example such as flow from a hopper or silo could also benefit from the following:
Shear Cell Testing (How much energy is needed to initiate flow in a consolidated or stressed state of the powder?)
Wall Friction Testing (How does flow energy change when different polished metal surfaces are in contact with the powder?)
The versatility of the Freeman FT4 Powder Rheometer has proven beneficial to numerous clients in the pharmaceutical, automotive, cement, cosmetic and industrial sectors. Please contact us to discuss how the FT4 Powder Rheometer may help provide additional solutions to your powder handling questions.
Larger sample volumes are preferred if possible, since we are evaluating bulk powder properties. Ideally, the lab requests around 1 liter to 1.6 liter of powder. This allows for larger vessel and fresh material for each test performed. However, if sample quantity is limited, PTL can work with as little as 450 mL while still using a fresh sample for each test. Please note the smaller sample size is not as robust a measurement as an analysis using the larger cell.
Questions on sample needs – please contact us to share specifics about your sample and options for suitable sample quantities.
With the Freeman FT4 Rheometer, a comprehensive summary of the 7 analyses included in a powder flowability study are provided – Basic Flow Energy, Variable Flow Rate, Effects of Compaction (Taping vs Direct Pressure), Aeration/De-Aeration, Compressibility, Permeability, and Conditioned Bulk Density. Results are reported graphically and numerically.
Particle Technology Labs has industry top players for powder testers with the Freeman Technology FT4 and Anton Paar MCR rheometers.
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