Extrusion of polymers and polymer blends with supercritical carbon dioxide

Extrusion of various polymers and polymer blends was carried out in the presence of supercritical carbon dioxide and the effects of the supercritical CO₂ on the viscosity and morphology of polymers and polymer blends were investigated. Various extrusion systems such as single-screw, twin-screw, and twin/single tandem extruders were utilized. In order to ensure a single-phase polymer/CO₂ solution, generating high pressure in extruders is essential, and special extruder setups equipped with an CO ₂ injection device and a secondary die were designed. The solubility of CO₂ in polymers and the density prediction of polymer/CO ₂ solutions were also studied.; Effects of supercritical CO₂ on the polymer viscosity was mainly studied in polystyrene/carbon dioxide solution system. The viscosity of PS/CO₂ solutions was measured on-line using a linear capillary tube die mounted on a single-screw foaming extruder and a wedge die mounted on a twin-screw extruder.; The effects of dissolved supercritical CO₂ on the viscosity and morphological properties of polyethylene/polystyrene blending systems were also investigated using a twin-screw extruder equipped with a wedge die. It was observed that the dissolution of CO₂ into PE/PS blends, regardless of the CO₂ content used, led to decreased shear thinning behavior.; A twin/single tandem extrusion system was designed for investigating the effects of dissolved supercritical CO₂ on the morphological properties of the PE/PS blends. In general, the mixing between two polymers was improved by the dissolution of CO₂.; Reactive extrusion of a polyethylene/polyamide-6/polyethylene-g-maleic anhydride system was performed in the presence of supercritical CO₂. Effects of the dissolved CO₂ and the polyethylene-g-maleic anhydride (PE-g-MAH) on the viscosity and the blending morphology were investigated in the tandem extrusion system. It was found that the addition of a small amount of polyethylene-g-maleic anhydride to polyethylene/polyamide-6 (PE/PA6) blends causes an increase of blend viscosity. (Abstract shortened by UMI.)...