Effects of an ionic liquid,1-n-tetradecyl-3-methylimidazolium bromide([C14MIM]Br),as a foaming additive on the foaming behavior of polypropylene(PP) by supercritical CO2 technique was reported.Mass ratio of PP/[C14MIM]Br up to 100∶10 was incorporated via melt blending.The melting behavior and fractured morphology of PP/[C14MIM]Br samples were investigated by differential scanning calorimetry(DSC) and scanning electron microscopy(SEM),respectively.The CO2 sorption was measured by commonly accep-ted gravimetric method.The results of DSC and CO2 sorption experiments show that [C14MIM]Br has little effect on the crystallinity,melting point and the mass uptake of CO2 of PP.SEM images reveal that [C14MIM]Br forms a well-dispersed phase,whose size increases with [C14MIM]Br content,in the PP matrix.The foamed PP/[C14MIM]Br samples exhibit close cell structure,increased cell size and decreased unfoamed region and bulk density,compared with pure PP foamed under the same saturation conditions of 155 ℃/10 MPa,indicating ionic liquid [C14MIM]Br has significant effect on the foaming behavior of PP.
