Prediction of Inter-particle Adhesion Force from Surface Energy and Surface Roughness

Passivation of High-Surface-Energy Sites of Milled Ibuprofen Crystals via Dry Coating for Reduced Cohesion and Improved Flowability

“…What further exacerbates this situation is the increased surface energy. [2][3][4][5][6] This leads to powder agglomeration, poor flowability, low bulk density, and solid bridging. [7][8][9] As a result, handling and processing of these powders become difficult.…”

“…[7][8][9] As a result, handling and processing of these powders become difficult. It is generally believed that the reason for increased surface energy upon milling is because of the relative exposure of newly created, higher energy crystal faces because of particle fracture/breakage, [2][3][4]6 and may also be caused by increased surface energy heterogeneity because of milling. 2 In a previous study, simultaneous micronization and dry coating achieved by the fluid energy milling (FEM) process 10 to mitigate the disadvantage of the poor bulk properties of the micronized powder were considered.…”

“…10 The extent of the flow improvements for very fine ibuprofen powders that were simultaneously dry coated as compared with uncoated ones was outstanding, for example, flow function coefficient (FFC; a significant measure of flow property based on shear testing 11 ) for 10 :m ibuprofen increased 10 from about 1 to 6, which is a significant achievement as compared with that observed in dry coating performed without micronization, [12][13][14][15][16] for example, similar sized acetaminophen powder had FFC of about 2 and after dry coating increased to a little over 3. 15,17 Thus, it appears that the flow improvement phenomena because of dry coating during milling may be somewhat different, and in addition to silica creating separation, or more precisely, nanoscale surface roughness, 3,13 it may also be reducing overall surface energy as well as surface energy heterogeneity via passivating high-surfaceenergy sites on milled ibuprofen powders, leading to significantly improved flow properties. Accordingly, the objective of this paper is to examine this intriguing possibility through a systematic investigation of the influence of dry coating on surface energy of milled pharmaceutical crystals, in particular, the reasons for very high cohesion of milled powders in contrast to the improvements observed after dry coating.…”

Powder Technology and Pharmaceutical Development: Particle Size and Particle Adhesion

“…The flowability of powders is affected by particle size [3][4][5] . In the case of small particle sizes, where the friction and adhesion forces between particles are important, flow decreases with decreasing particle size.…”

“…The opposite is true when gravitational forces dominate. Jallo and co-workers, in particular, have considered the relation between interparticle adhesion and a measure of flowability 5) .…”