Effect of Talc on the Cell-Population Density of Extruded Polypropylene Foams

Abstract

The effect of talc on the cell morphology of polypropylene (PP) foams has been investigated. A branched high-melt-strength PP was used in this study to reduce the bubble coalescence phenomenon during the foam processing in extrusion with isopentane or CO2 as a blowing agent. When isopentane was processed with PP, the bubble nucleation in the extruded foams was dominated by the talc concentration, and the isopentane content did not strongly affect the cell-population density. However, when CO2 was used as the blowing agent, both the talc concentration and the CO2 concentrations played an important role in determining the cell-population density. Although previous studies on the foam processing with CO2 alone indicated that the cell-population density was a strong function of the processing pressure and the pressure-drop rate, neither of these processing parameters significantly influenced the cell morphology of the extruded PP foams when talc was employed as a nucleating agent.