Introduction of the energy to break an avalanche as a promising parameter for powder flowability prediction
Dynamic avalanche testing is a newer method useful even with cohesive powder samples. To evaluate flow properties of pharmaceutical powder excipients, break energy (BE) is introduced as a new promising avalanche parameter. Conventional pharmacopoeial methods and an annular shear cell were utilized to characterize 23 pharmaceutical powder samples including binary mixtures.
• Orifice discharge by gravity does not operate well for highly porous materials.
• Avalanching in a rotational drum allows measurement of even problematic materials.
• Breaking the interparticle forces induces an avalanche as a relevant bulk property.
• Break energy of the avalanche (BE) showed a good correlation with cohesion.
• BE reflects well the interruption of particle-particle interactions in a powder bed.
Subsequently, rotating drum avalanching was studied to better understand behaviour of powders. A good linear regression between the energy to break a powder avalanche and powder cohesion with R2 = 0.823 was detected. The relationship between BE and the flow function value, estimated by shear testing, allowed to identify two samples with excellent flow functions: Cellets 100 and Neusilin US2. The latter sample also had very low BE although the mass flow rate was the poorest observed out of 23 samples. Therefore, the BE from avalanching testing seems to be a sensitive measure of cohesion and flow function behaviour. More on Introduction of the energy to break an avalanche as a promising parameter for powder flowability prediction
Keywords: powder, flowability, amorphous magnesium alumino metasilicate Neusilin® US2 ), sorbitol for direct compaction Merisorb® 200, Excipress™ GR150, GranuLac® 70, Lactopress® Anhydrous, Lactopress® Granulated, SpheroLac® 100, Tablettose® 80, Powder microcrystalline cellulose Comprecel® , Microcrystalline Cellulose 102, pellets made of microcrystalline cellulose Cellets® 100