Operating regimes and mechanism of particle formation during the precipitation of polymers using the PCA process

This article provides experimental evidence for the hypothesis that when processing polymer solutions there are two different mechanisms of droplet formation governing the final size of the precipitated polymer particles: hydraulic atomisation and liquid-liquid phase split. The system l-polylactic acid (l-PLA)-dichloromethane (DCM)-CO2 was used to demonstrate that particle size can be manipulated by modifying the operating conditions. Working at conditions below the mixture critical pressure of the solvent-CO2 mixture it was possible to produce polymer particles in the range of 5-50 μm. At conditions where the two fluids are completely miscible, l-PLA particles ranging from 0.1 to 2 μm and microfibers were obtained. The possibility of co-precipitation of cholesterol and l-PLA was also addressed.