in the extruder and fed at a rate of 100 kg per hour through the static mixer at a temperature of 240 u00b0 c the pressure at the inlet of the static mixer was 15 mpa 150 barg the stripping agent used was a 1 0 by weight solution based on the total weight of solution of carbon dioxide in water which was injected continuously into the molten polymer stream at a rate of 1 0 by weight of the polymer flow rate the pressure in the flash tank was held at 20 mmhg 26 66 u00d7 10 2 pa polystyrene polymer removed from the system having undergone devolatilisation and pelletising was found to have a residual styrene monomer content measured by means of gas chromatography of 50 ppm the procedure of example 1 was repeated but instead using water alone i e with no dissolved carbon dioxide as the stripping agent the residual styrene monomer content in the devolatilised polymer was found to be 150 ppm the procedure of example 1 was repeated except that deaerated water i e without any dissolved carbon dioxide was used as the stripping agent the residual styrene monomer content in the devolatilised polymer was found to be 160 ppm the procedure of example 1 was repeated but instead of using 1 0 by weight based on the weight of polymer of carbon dioxide alone with no water as the stripping agent the residual styrene monomer content in the devolatilised polymer was found to be 160 ppm the procedure of example 1 was repeated but using 0 1 by weight based on the weight of polymer of carbon dioxide alone with no water as the stripping agent the residual styrene monomer content in the devolatilised polymer was found to be 500 ppm the procedure.