Fabrication of Polypropylene Composite Open-Cell Foams and Repetitive Oil Absorption Performance
Polypropylene(PP),polystyrene(PS)and carboxylated multi-walled carbon nanotubes(MWCNT-COOH)were melt-blended using a twin-screw extruder in this study.Supercritical carbon dioxide(scCO2)foaming technology was then used to prepare PP-based composite foams with high foaming ratio and high open-cell content for oil-water separation applications.The microscopic structures,viscoelasticity,crystallinity,foaming behaviors,and repetitive oil absorption performance of the PP-based composites were characterized through morphology,rheology,differential scanning calorimetry(DSC),scCO2 foaming and repetitive oil absorption tests.The results show that PS and MWCNT-COOH can synergistically enhance the melt strength of PP matrix.Compared with PS,MWCNT-COOH exhibits stronger promotion effect on PP crystallization.Under the synergistic heterogeneous nucleation function of PS and MWCNT-COOH,the PP-based syntactic foam containing PS with a mass fraction of 10%and MWCNT-COOH with a mass fraction of 1%exhibits a cell density of 4.5×108 cells/cm3,a foaming ratio of 22.5 and an open-cell rate of 89%.Besides,its maximum oil absorption capacities for silicone and cyclohexane are respectively 19 g/g and 13.4 g/g.Even after 10 compression cycles,the permanent deformation of the foam retains only 25%,and the oil absorption capacities for silicone and cyclohexane still maintain at 13.8 g/g and 10.1 g/g,respectively.
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