(400aa) Using Magnetically Assisted Impact Coating (MAIC) to Improve Powder Flow Parameters

Many powders resist flowing and have poor basic flow properties. These poor properties manifest themselves in problems with pneumatic conveying, fluidization, and filling of dies. Powders can further exhibit problems upon storage, where consolidation and caking can further reduce the flow properties of a powder.

In order to provide more consistent processing and product quality, flow aids, such as fumed silica or magnesium stearate, are typically added to a powder to improve its flow and/or reduce its tendency to cake. These flow aids are typically added via a traditional blending method, such as v-blending, with the amount of flow aid being the only processing parameter that could be used to control changes in powder flow. Unfortunately, most processes have an inherent maximum amount of flow aid that can be added before product quality is affected. Frequently, the maximum is also governed by regulatory statues.

In a preliminary study [1], Magnetically Assisted Impact Coating (MAIC) was shown to improve flow properties of a model compound, 5 μm citric acid, when compared with a traditional blending process, v-blending. The initial study was done with an FT4 Powder Rheometer® comparing fumed silica loadings of 0.5% and 2.0% (w/w), and showed that for a number of powder flow parameters, MAIC-processed material had better flow properties than that of v-blended material. This follow-up study verifies the original findings and expands it to include 0.0%, 0.5%, 1.0%, 2.0%, and 5.0% (w/w) silica loadings, and presents statistical comparisons between the flow properties of v-blended samples and MAIC-treated samples, including flow parameters not studied or well characterized in the initial study [2].

The result of the this study shows that MAIC improves flow properties of the model compound at all levels of flow aid addition, which allows for further improvement of flow properties or a reduction in the needed levels of flow aid for equivalent powder flow. MAIC was even shown to improve flow properties when no flow aid was added; the reason for this is still under investigation.

References

[1] Freeman, T; Hendrickson, W.; Bowman, C. R. et al. (2016, November). Comparison of Magnetically Assisted Impact Coating (MAIC) with Traditional Mixing Techniques for the Addition of a Silica Flow Aid. Paper presented at the meeting of the American Institute of Chemical Engineers, San Francisco, CA.

[2] Brockbank, K., Armstrong, B., Chandorkar, Y., et al., Understanding powder caking as a consequence of a range of mechanisms by means of powder rheometry. 2015:33:102-108.