title: A Simplified Model of Moisture Transport in Hydrophilic Porous Media With Applications to Pharmaceutical Tablets.
abstract: This work establishes a predictive model that explicitly recognizes microstructural parameters in the description of the overall mass uptake and local gradients of moisture into tablets. Model equations were formulated based on local tablet geometry to describe the transient uptake of moisture. An analytical solution to a simplified set of model equations was solved to predict the overall mass uptake and moisture gradients with the tablets. The analytical solution takes into account individual diffusion mechanisms in different scales of porosity and diffusion into the solid phase. The time constant of mass uptake was found to be a function of several key material properties, such as tablet relative density, pore tortuosity, and equilibrium moisture content of the material. The predictions of the model are in excellent agreement with experimental results for microcrystalline cellulose tablets without the need for parameter fitting. The model presented provides a new method to analyze the transient uptake of moisture into hydrophilic materials with the knowledge of only a few fundamental material and microstructural parameters. In addition, the model allows for quick and insightful predictions of moisture diffusion for a variety of practical applications including pharmaceutical tablets, porous polymer systems, or cementitious materials.
authors.affiliation: Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104.
authors.forename: Gerard R
authors.initials: GR
authors.lastname: Klinzing
authors.affiliation: Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104. Electronic address: azavalia@coe.drexel.edu.
authors.forename: Antonios
authors.initials: A
authors.lastname: Zavaliangos
mesh_terms: D002482:Cellulose / Q000737:chemistry; D004058:Diffusion; D006813:Humidity; D057927:Hydrophobic and Hydrophilic Interactions; D008855:Microscopy, Electron, Scanning; D008962:Models, Theoretical; D016062:Porosity; D013499:Surface Properties; D013607:Tablets / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D013607:Tablets; D014867:Water; D002482:Cellulose; C109691:microcrystalline cellulose
keywords: humidity; hydrophilic materials; moisture diffusion; porous materials; transient effects