Effect of CO ₂ Content on Foaming Behavior of Recyclable High-Melt-Strength PP

This paper presents an experimental study on the foaming behavior of recyclable high-melt-strength (HMS) branched polypropylene (PP) with CO₂ as a blowing agent. The foamability of branched HMS PP has been evaluated using a tandem foaming extruder system. The effects of CO₂ and nucleating agent contents on the final foam morphology have been thoroughly investigated. The low density (i.e., 12~14 fold), fine-celled (i.e., 10⁷–10⁹ cells/cm³) PP foams were successfully produced using a small amount of talc (i.e., 0.8 wt%) and 5 wt% CO₂.