Study On Extruding Polytetrafluoroethylene /Polypropylene Assisted By Supercritical CO₂

Supercritical carbon dioxide has been widely used in preparing and modifying macromolecular materials.In this paper, extruding and modifying PTFE were studied by use of supercritical CO₂ and mix with PP and the continuous extrusion of PTFE through a twin-screw extruder was realized. Influence of supercritical CO₂ on rheological properties and mechanical properties of macromolecular materials system in extrusion process was researched. Results show that the continuous extruding PTFE is realized by use of supercritical CO₂ and PP. Addition of PP improves feeding and melting of PTFE during extrusion. Addition of supercritical CO₂ can reduce melt viscosity, depress extrusion pressure effectively and advance extrusion efficiency obviously. Supercritical CO₂ can make polymer high yield extrusion under low pressure.The addition of supercritical CO₂ can improve fluidity of polymer melt obviously, extend the process range and be useful of macromolecule extrusion. With the increase of PTFE content in the PTFE/PP blend, the effectiveness of melt viscosity reduction is obvious. So the effectiveness of macromolecular melt viscosity reduction effected by supercritical CO₂ is obvious.Mechanical properties results show that the tensile strength and elongation at break of PTFE/PP blend effected by supercritical CO₂ is lower than what isn't effected by supercritical CO₂, but the toughness of PTFE/PP blend enhance obviously.