Effects of Blend Morphology on the Foaming of Polypropylene/ Low-density Polyethylene Blends during a Batch Foaming Process

Abstract

The effect of blend morphology on the foaming of polypropylene (PP)/low-density polyethylene (LDPE) blends with different blend ratios has been studied in this work. The results showed that the cell morphology of a foamed blend was significantly impacted by the blend morphology and foaming conditions. When the foaming temperature was close to the melting temperature of LDPE, cells were nucleated at the interfaces of PP droplets and LDPE matrix in the 10/90 and 25/75 PP/LDPE blends and grew in the LDPE matrix. Also, cells could only grow in the LDPE phase in the 90/10 and 75/25 PP/LDPE blends and consequently their sizes were determined by the sizes of the LDPE droplets. However, when the foaming temperature was close to the melting temperature of PP, cells with bimodal cell size distributions were generated in the pure PP, 90/10 and 75/25 PP/LDPE foams. In particular, fine open-cell structure was formed in the co-continuous 50/50 PP/LDPE blend.