In-situ Observation on Foaming of Molten Polypropylene by Supercritical Carbon Dioxide
Hideo Ohyabu, Katsuto Otake, Hiromichi Hayashi, Hiroshi Inomata
Joint Research Center For Supercritical Fluids Japan Chemical Innovation Institute(JCII),National Institute of Advanced Industrial Science and Technology
JAPAN
Keywords: foaming, polypropylene, visualization
In order to clarify the factor governing a foaming process, the bubbling behavior of polypropylene(PP)-supercritical carbon dioxide was directly observed using the high pressure visualization device which was originally developed for this study. The results revealed that the distinct foam generation occurred under high-pressure conditions of carbon dioxide. From these visualization results observed with motion pictures, various foaming behaviors were quantitatively analyzed, regarding the influence of pressure, temperature and de-pressurization rates, and the influence of the decompression speed on foaming in a batch process was quantitatively clarified (threshold value). Moreover, the animated visualization on foaming behaviors could give us the easy understanding on the relationship between the growth of bubbles and the decompression speed changes in the molten state. It suggested that the decompression speed plays a very important role to control the cell size in the molten polymer.