Formation and Coatings of Fine Particles in Jets of Supercritical Fluids
A. Gokhale, Y. Shen, B. Khusid, R. Dave and R. Pfeffer
New Jersey Institute of Technology, US
nanoparticles, coating, polymer, jets, micro-nozzles, supercritical fluids, solvents
Recently published studies of the formation of polymer particles in supercritical carbon dioxide are limited to the use of good organic solvents or their mixtures and relatively wide nozzles. In contrast, we use the new concept of mixing “good” and “poor” solvents and micro-nozzles to regulate the precipitation of a polymer from the injected solution. The Raleigh and Weber regimes of the jet breakup were found to suppress the particle aggregation and, therefore, favor the formation of Polyvinylpyrrolidone nano-powders, having narrow particle size distribution. Increasing the operational pressure well above the critical point was shown to increase the average size of the polymer particles and broaden the particle size distribution. Coating of nanometer and sub-micrometer silica particles for the modification of their surface was achieved by the use of our proprietary coaxial ultrasonic nozzle. Utilizing the concept of a mixture of “good” and “poor” solvents, we were able to coat the silica particles with Eudragit which is widely used in the pharmaceutical and fine chemicals industries.
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Nanotech 2006 Conference Program Abstract