Abstract: Isotactic PP (iPP) was grafted with polystyrene using benzoyl peroxide (BPO) as an initiator, and simultaneously mixed with a nucleating agent ［1,3:2,4bis(p-methylbenzylidene) sorbitol; MDBS］ through melt extrusion. The effect of MDBS on the foaming behavior of the grafted PP was investigated. The styrene grafting decreased the melt flow rate of iPP and increased its melt strength. MDBS could hold the cell structure and acted as a cell nucleating agent during foaming. The cell density increased from 1.1×10^7 for neat iPP to 1.2×10^8 cells/cm3 for grafted iPP, and the suitable foaming temperature range was broadened to 150~160 ℃.

Key words: polypropylene, styrene, grafting reaction, 1, 3:2, 4-bis(p-methylbenzylidene) sorbitol, foaming