Viscosity reduction of polymers by the addition of supercritical carbon dioxide in polymer processing

The viscosity of a polymer often dictates the manner in which a polymer is processed, as well as the end use capabilities, mechanical strength and cost. As the viscosity of polymers is increased so is the energy required to process them. Plasticizing agents are often added to high viscosity materials to aid in processing. Supercritical carbon dioxide, scCO₂, can be added to polymer melts to lower their viscosity. In this work scCO₂ is injected into the barrel of a Haake single screw extruder with a 3/4 inch screw and L/D = 25 that is processing polystyrene. This technique results in a substantial drop in polymer melt viscosity as is measured by a slit die rheometer attached to the single screw extruder.