Evonik-Degussa needed to develop a new and repeatable testing procedure to more accurately gauge the effects of its AEROSIL and SIPERNAT silicas on the caking and flow properties of powdered products in the food, feed, pharmaceutical and chemical industries. Powders containing silica are much more free-flowing than standard powders and granules. Even compressed samples are relatively unstable and easy to disturb during loading onto testing instrumentation. Tackling this challenge, Evonik-Degussa’s applications experts developed a patented adapter that allows the prepared sample to be loaded onto the powder flow analyzer while still mounted on the teflon sheet. This avoids any potential damage to the compacted structure before the test begins.
Previously, Evonik-Degussa’s powder assessment was conducted with a manual “caking” test that involved compressing a powder sample within a hollow metal cylinder using a solid metal cylinder. The sample was stored on a teflon sheet under defined heat, humidity and pressure conditions to create a tablet shape. Once the “tablet” was formed, both cylinders were removed and pressure was applied with a human finger. Its ability to withstand this force was measured subjectively using a simple scoring system (1-6). While useful, this test procedure was limited because of its lack of repeatability and objectivity of the manual test.
The new procedure test is conducted with a newly designed powder cartridge. Sample preparation and storage is identical to the old test but now the solid metal cylinder and teflon plate are removed. This means that powders’ properties can be tested whether or not they had formed self-supporting structures during storage. Aeration, compaction, and slice compaction tests provide valuable data on powders’ surface friction properties, mixing kinetics, cohesiveness and flow and recovery properties.
The powder flow analyzer’s patented rotating blade is programmed to pass through the sample in a particular way, for a fixed number of rotations, according to the individual test requirements. As this happens, a loadcell measures the sample’s resistance to flow. As it is common to find a “crust” on the surface of a compressed sample, Evonik-Degussa can now identify differences in force as the blade moves downwards through the powder. Similarly, the test procedure provides data on quantify differences in the properties of samples containing varying levels of flow agents, including samples containing no silica at all.
The new test allows the identification of the most appropriate flow agent for a particular application and subsequently the specification of addition levels to control clumping and crusting behavior. It also facilitates maintaining free-flowing powders that are easier to handle and process.
The Powder Flow Fixture for the TA.XTPlus Texture Analyzer is part of the extensive line of probes and fixtures available from Stable Micro Systems.
Are you looking to improve your testing procedures for powders? Contact us and we can help you evaluate what procedures will provide you with methods that you want.
