title: Fine powder flow under humid environmental conditions from the perspective of surface energy.
abstract: The influence of humidity on surface energetics and flow behavior of fine pharmaceutical powders was investigated. Amorphous and crystalline fine powders with hydrophilic (Corn starch and Avicel PH105) and hydrophobic (ibuprofen) nature were considered for this study. The surface energy was determined using surface energy analyzer and flow behavior was measured in terms of unconfined yield stress (UYS) using a shear tester. The study showed that unlike hydrophobic ibuprofen powder, surface energy and flow of hydrophilic excipient powders were affected by relative humidity (RH). The Lifshitz-van der Waals dispersive (γ(LW)) component of surface energy barely changed with varying RH for all pharmaceutical powders. For hydrophilic excipients, the specific component of surface energy (γ(SP)) was found to increase with increasing RH. Furthermore, for these excipients, flow deterioration at elevated RH was observed due to increased capillary bridge formation. Detailed analysis showed that γ(SP) component of surface energy can be an effective indicator for flow behavior of fine powders under varying humid conditions. The present study also brought out the existence of different regimes of probable interparticle forces which dictate the bulk flow behavior of fine hydrophilic powder under humid conditions.
authors.affiliation: DryProTech Lab, Chemical Engineering, Indian Institute of Technology Gandhinagar, VGEC Campus, Chandkheda, Ahmedabad, Gujarat 382424, India.
authors.forename: Vikram
authors.initials: V
authors.lastname: Karde
authors.affiliation: DryProTech Lab, Chemical Engineering, Indian Institute of Technology Gandhinagar, VGEC Campus, Chandkheda, Ahmedabad, Gujarat 382424, India. Electronic address: chinmayg@iitgn.ac.in.
authors.forename: Chinmay
authors.initials: C
authors.lastname: Ghoroi
mesh_terms: D002482:Cellulose / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D018360:Crystallography, X-Ray; D005079:Excipients / Q000737:chemistry*; D006813:Humidity; D057927:Hydrophobic and Hydrophilic Interactions; D007052:Ibuprofen / Q000737:chemistry*; D010316:Particle Size; D011208:Powders; D012212:Rheology; D013213:Starch / Q000737:chemistry*; D013499:Surface Properties; D013678:Technology, Pharmaceutical / Q000379:methods*; D014867:Water / Q000737:chemistry*; D017155:Wettability
chemical_list: D005079:Excipients; D011208:Powders; D014867:Water; D002482:Cellulose; D013213:Starch; D007052:Ibuprofen
keywords: Humidity; Interparticle force; Moisture sorption; Pharmaceutical powders; Powder flow; Surface energy