Development of a strategy for the foaming of polystyrene dissolutions in scCO2

Interfacial tension (IFT) is a key physicochemical parameter that plays an important role during the foaming process of polymers. The pendant droplet method is a useful technique to determine the IFT, which has been studied at mild working conditions (0–9 MPa, 303.15–313.15 K). In this work, limonene and cymene were used as solvent to prepare polymer dissolutions and observe their influence on the experimental IFT measurements. Also, the effect of CO2 on the glass transition of polystyrene and polystyrene dissolutions was studied in order to select the most suitable temperature to carry out the experiments. The behaviour of the polystyrene dissolution in the presence of CO2 can be considered similar to molten polymer. A controlled foaming of the polystyrene-solvent mixtures can be easily carried out at moderate temperature and pressures by exploiting the advantages that provide the solvent, obtaining completely “dried” PS foams.