(418ad) Effect of Humidity on Bulk Properties and Surface Energetics of Fine Powders

Humid environment often creates various problems in fine powder processing and frequently pose substantial threat to the final product quality.The present study focuses on the effect of humidity on bulk behavior and surface energeticsof fine pharmaceutical excipient powder with and without surface modification. Corn starch powder was surface modified using Aerosil R972 type hydrophobic nano-silica through dry coating. Bulk property characterization for uncoated and surface modified powders was carried out using FT4 powder rheometer. It was found that flow and packing properties of uncoated powder deteriorated with increasing relative humidity (% RH) and prominent changes were observed above 60% RH. In contrast, these bulk properties of surface modified powders were found to be more or less consistent and stable. Further, in order to understand these changes in bulk behavior of powder, surface energy studies of humid powders were carried out using Inverse Gas Chromatography (IGC). IGC studies revealed that both dispersive and specific components of surface energies of uncoated corn starch powder changes with changing humidity conditions from 30% to 90%.On the other hand, surface energies of dry coated powders remained more or less constant at different range of humidity conditions studied. The present study showed that surface modification of powders helped to prevent the detrimental effects of humidity on bulk behavior and surface energetics of fine powders.