Dissolution of Atmospheric Gases in Polystyrene Melt in Single and Twin-Screw Foaming Extruders

Abstract

Dissolution and solubility characteristics of carbon dioxide in polystyrene melt were studied in both single screw and twin-screw foaming extruders. The effects of the main processing conditions on the gas dissolution behavior were also studied. Solubility data obtained from the twin-screw extrusion experiments showed better consistency compared with those obtained from the single screw experiments, indicating the importance of enhanced mixing in affecting the gas dissolution and solubility behavior during an extrusion foaming process. Gas dissolution inside a single screw foaming extruder was studied for three atmospheric gases (carbon dioxide, nitrogen and argon) in polystyrene melts. The results were compared with those obtained in a twin-screw extruder for the carbon dioxide-polystyrene system in an effort to elucidate mechanisms for the complex process of gas dissolution inside a foaming extruder.

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