Effect of process conditions on the spray characteristics of a PLA+methylene chloride solution in the supercritical antisolvent precipitation process

Mechanisms controlling supercritical antisolvent precipitate morphology

“…In the case of miscible fluids (liquid and CO 2 mixture above the mixture critical point), they observed that liquid droplets never form, because the surface tension vanishes before that the jet break-up occurs. Successively, Sarkari et al [13], Dukhin et al [25], Badens et al [26], Gokhale et al [27], and Obrzut et al [28] studied the jet atomization in pressurized gases, observing that turbulent single-phase mixing dominates at completely developed supercritical conditions. It was also observed that the transition between multi-phase (formation of droplets after jet break-up) and singlephase mixing (no formation of droplets) takes place at pressures slightly above the mixture critical pressure (MCP).…”

Hydrodynamics Influence on Particles Formation Using SAS Process

“…Lee et al injected a solution of dichloromethane (DCM) and poly lactic acid (PLA) at subcritical conditions in the dripping and in the Rayleigh disintegration regimes and observed the formation of uniform PLA microparticles . Other authors (Chang et al, 2008;Gokhale et al, 2007;Obrzut et al, 2007;Reverchon et al, 2008) did not find relevant differences in the various precipitates obtained. Particularly, PLA morphologies showed to be insensitive to the SAS processing conditions (Randolph et al, 1993).…”

“…Jet lengths and spray widths ranging to milimeters and drop and particle sizes ranging to micrometers must be taking into account in order to select imaging system components. Several studies used particle and droplet visualization in supercritical fluids (Badens et al, 2005;Gokhale et al,2007;Kerst et al,2000;Lee et al,2008;Mayer & Tamura,1996;Obrzut et al,2007;Randolph, et al, 1993;Shekunov et al, 2001). The optical technique described in these works provides the ability to visualize mixing occurring between two fluids with different refractive indices.…”

Formation of MPEG-PLLA block copolymer microparticles using compressed carbon dioxide

“…Weidner et al [24] have reported that the melting point of PEG 4000 decreases significantly with increasing pressure, especially up to 80 bar (from 56.2 o C at 1 bar to 45 o C at 80 bar) and is practically constant in the pressure range of 80-210 bar. In contrast, many researchers have confirmed that well-formed particles of the semicrystalline PLLA are produced by the ASES processing using SCCO 2 as antisolvent [7,10,11,25]. Thus, it is very plausible that the particles collected on the metal filter at the bottom of the precipitator have aggregated in the supercritical region.…”

“…Furthermore, these methods usually require a post-production drying step, lasting several days, to remove the residual solvent. To overcome these limitations, many innovative particle engineering techniques have been developed, among which supercritical fluid technology is one of the most promising methods [7][8][9][10][11].…”