Abstract:

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 un-foamed 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.

Key words: [C14MIM]Br ionic liquid; Polypropylene; Supercritical carbon dioxide; Foaming property