Dissolution kinetics of polymer powders

The dissolution kinetics of polymer powders as isolated grains or in beds w ere studied theoretically and experimentally. A simple model developed for the dissolution of a dispersion of isolated grains with an arbitrary size d istribution was confirmed experimentally using polysaccharides in water. Ba sed on experimental data for the dissolution of lump-forming powder beds, m odeled using a bimodal population of grains and lumps, a robust technique w as developed for analyzing experimental data, which is independent of the d etails of lump formation. A qualitative picture of lump formation is descri bed, based on the idea that during the initial hydration of a powder bed a "pore blocking" condition quickly develops due to the formation of a gel la yer around the dry grains. Once formed, lumps dissolved the same way and wi th the same kinetic description, as individual, dispersed grains.