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Preparation of microcellular polypropylene/polystyrene blend foams with tunable cell structure
Author(s) -
Huang HanXiong,
Xu HongFei
Publication year - 2011
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.1584
Subject(s) - materials science , polypropylene , polystyrene , composite material , morphology (biology) , polymer blend , cell size , supercritical carbon dioxide , phase (matter) , supercritical fluid , chemical engineering , copolymer , polymer , chemistry , genetics , organic chemistry , engineering , biology , microbiology and biotechnology
By using supercritical carbon dioxide (sc‐CO 2 ) as the physical foaming agent, microcellular foaming was carried out in a batch process from a wide range of immiscible polypropylene/polystyrene (PP/PS) blends with 10–70 wt% PS. The blends were prepared via melt processing in a twin‐screw extruder. The cell structure, cell size, and cell density of foamed PP/PS blends were investigated and explained by combining the blend phase morphology and morphological parameters with the foaming principle. It was demonstrated that all PP/PS blends exhibit much dramatically improved foamability than the PP, and significantly decreased cell size and obviously increased cell density than the PS. Moreover, the cell structure can be tunable via changing the blend composition. Foamed PP/PS blends with up to 30 wt% PS exhibit a closed‐cell structure. Among them, foamed PP/PS 90:10 and 80:20 blends have very small mean cell diameter (0.4 and 0.7 µm) and high cell density (8.3 × 10 11 and 6.4 × 10 11 cells/cm 3 ). Both of blends exhibit nonuniform cell structure, in which most of small cells spread as “a string of beads.” Foamed PP/PS 70:30 blend shows the most uniform cell structure. Increase in the PS content to 50 wt% and especially 70 wt% transforms it to an irregular open‐cell structure. The cell structure of foamed PP/PS blends is strongly related to the blend phase morphology and the solubility of CO 2 in PP more than that in PS, which makes the PP serve as a CO 2 reservoir. Copyright © 2009 John Wiley & Sons, Ltd.