Abstract: Influence of types, particle sizes, and dosages of nucleating agent on the cell structure of the batch foaming of polypropylene with supercritical carbon dioxide was investigated. When calcium carbonate was used, better cell integrity and more uniform cell size distribution, and higher expansion ratio were obtained compared with the foam using talc and montmorillonite. The smaller the particle size, the more the nucleation sites, and the larger the cell density. A loading of 3 phr calcium carbonate was optimal to achieve high expansion ratio and cell density.

Key words: polypropylene, nucleating agent, batch foaming process, cell structure