Abu-Khalil, As'ad Abdul-Lateef; (1999) The influence of lubricants and glidants on the flow and capsule filling properties of powders. Doctoral thesis (Ph.D.), University College London (United Kingdom).

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Abstract

The effect of lubricants and glidants on the flow properties of different diluents and its relation to capsule filling performance has been investigated. The flow properties of powders and blends were assessed using an annular shear cell and a jolting volumeter. The annular shear cell was also used to measure the powder-wall friction using two plates of different roughness. The capsules were filled with a dosing tube capsule filling machine. The evaluation of the capsule filling performance was based on the resultant mean fill weight of the capsules and their weight variation. The effect of the lubricants and glidants on the flow properties of the diluents was found to be more dependent on the properties of the latter than the former. From the different types of the lubricants investigated, the fatty acid derivatives performed better, even at small concentrations, than the other types such as, microcrystalline cellulose and talc. The lubricant particle size was shown not to be important as long as there is sufficient lubricant present at the sliding interface. The angle of wall friction failed to predict the performance of powders in the process of capsule filling especially for blends with microcrystalline cellulose, Aerosil and talc. Critical values of the powder flow parameters were identified below or above which the powder blend produced an acceptable capsule filling performance. These powder flow parameters included, the Jenike flow function (ff), Carr's Compressibility Index (CCI), Kawakita's constants a and 1/b. The bulk property measurements were related more to the coefficient of variation of the fill weight and were more predictable of the performance of the powder in the process of capsule filling than the shear cell test measurements. The two most important factors to ensure a reproducible capsule filling were identified as, 1) a uniform powder bed and 2) a smooth ejection of the powder plug from the dosator nozzle.

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