Solubilities of sub-and supercritical carbon dioxide in polyester resins Nalawade, SP; Picchioni, F; Janssen, LPBM; Patil, VE; Keurentjes, JTF; Staudt, R; Nalawade, Sameer P.; Patil, Vishal E.; Keurentjes, Jos T.F. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum.

The major advantage of using supercritical carbon dioxide (CO 2 ) as a solvent in polymer processing is an enhancement in the free volume of a polymer due to dissolved CO 2 , which causes a considerable reduction in the viscosity. This allows spraying the polymer melt at low temperatures to produce micron size particles. We have used supercritical CO 2 as a solvent for the generation of particles from poly(ethylene glycol) (PEG) of different molecular weights. Since PEG is a hydrophilic compound, it is a most commonly used polymer for encapsulating a drug. PEG particles with different properties may allow keeping a good control over the release of the drug. It has been possible to produce particles with different size, size distribution, porosity and shape by varying various process parameters such as molecular weight, temperature, pressure and nozzle diameter. A flow and a solidification model have been applied in order to have a theoretical insight into the role of different parameters. ᭧

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The dissolution of CO 2 in a polymer causes plasticization of the polymer and hence, its viscosity is reduced. A model based on the free volume theory has been used for a polyester resin, which shows a considerable reduction in the viscosity due to dissolved CO 2. Therefore, supercritical CO 2 has been used as a processing solvent in the continuous production of micron size particles of the resin. Despite the viscosity reduction caused by the dissolved CO 2 , an excess quantity of CO 2 with respect to its solubility limit has been used for micronisation of the polymer due to its high viscosity. The mixing of CO 2 and the polymer has not been possible in an extruder at high gas to polymer mass ratios and consequently, a simplified Kenics type static mixer has been used for the mixing purpose. In this study, the effect of various parameters such as temperature, pressure, nozzle diameter and gas to polymer mass ratio on the particle morphology and size has been studied. The experimental results manifest the technological as well as the theoretical insight into the particles production from a high viscosity material.

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