Profoundly improving flow properties of a cohesive cellulose powder by surface coating with nano‐silica through comilling

Poor flow properties hinder the easy handling of powders during industrial‐scale processing. In this work, we show that powder flow can be substantially improved by reducing the cohesion of powders by coating them with nanosized guest particles. We further show that comilling is an efficient process for nanocoating. We have systematically investigated the effects of total number of comilling cycles (10-70 cycles) and silica loading (0-1.0 wt %) on the flow behavior of a highly cohesive and poorly flowing grade of microcrystalline cellulose powder (Avicel PH105). Optimum flow enhancement has been achieved with 1.0 wt % silica loading at 40 comilling cycles. The flow properties of nanocoated Avicel PH105 are comparable to those of Avicel PH102, which exhibits adequate flowability for processing on a high‐speed tablet press. Comilling is fast and suitable for continuous processing. It shows potential for addressing industrial powder handling problems caused by poor powder flow properties. © 2011 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:4943-4952, 2011