In this study, foaming behaviors of polyetherimide (PEI)/polypropylene-graft-maleic anhydride (PPMA) blends with different fractions of PPMA are investigated by the microcellular injection molding (Mucell) using N2 as the blowing gas. The results indicate that the addition of PPMA can obtain more the interface in blends than PP. Meanwhile, the microcellular PEI/PPMA foams achieve higher void fraction and cell density than that of PEI/PP and neat PEI matrix, and then the cell diameter also significantly decreases from 30 µm to less 10 µm. The excellent cell properties can be attributed to interfacial effect of binary blends. The binary interface decreases the nucleation energy barrier and forms sufficient paths which improve diffusibility of blowing gas, so the microcellular PEI/PPMA foams obtain more nucleating points and paths of supporting cell growth.
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