This article 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 characteristics have been thoroughly investigated. 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.
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