Extrusion Foaming of High Melt Strength Polypropylene
Christopher Stephen, Rahul Gupta, Sati N. Bhattacharya, H Lau
RMIT University
Australia

Keywords: PP, Foam, Extrusion

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High Melt Strength Polypropylenes (HMS PP) are versatile in foam extrusion processes because of their broader processing window. Exhibiting strain hardening properties under an extensional deformation, they are known to prevent premature cell coalescence and help produce close cell structures unlike linear Polypropylene.

HMS PP from Borealis is foamed using liquid CO2 as the blowing agent in the absence of external nucleating agents. The macro cellular foam extrusion is carried out in a single screw extruder and gas injection is by a syringe pump.

This study describes the foam extrusion process variables of the PP-CO2 system and their influence on the foam density and cell density.