EFFECTS OF SUPERCRITICAL CARBON DIOXIDE ON PE/PS BLEND VISCOSITY AND MORPHOLOGY

摘要

The effects of dissolved supercritical carbon dioxide on the viscosity and morphological properties were investigated for polyethylene/polystyrene blends in a twin-screw extruder. The viscosities of the blend/CO_2 solutions were measured using a wedge die mounted on the extruder. A considerable reduction of viscosity was found when CO_2 was dissolved in the blend. It was observed that the dissolution of CO_2 into PE/PS blends, regardless of the CO_2 content used, led to decreased shear thinning behavior resulting in an increase of the power law index. The cell structures of foamed PE/PS blends showed a typical dependence of pressure and CO_2 concentration, with higher operating pressures and CO_2 content leading to a smaller cell size. Also, it was noted that the size of the dispersed PS phase in the PE/PS blends decreased by increasing the CO_2 concentration, and that the dispersed PS phase domains were highly elongated in the direction normal to the cell radius.