pps proceeding - Abstract Preview
pps proceeding
Symposium: Foams & Lightweight Structures
Keynote Presentation
 
 

Visualization of Crystallization in Extrusion Foaming of Polypropylene

Tabatabaei Alireza (1), Park Chul B. (1)*

(1) University of Toronto - Ontario - Canada

Using a laboratory tandem foam extrusion system equipped with an adapter and a high pressure/temperature visualization chamber, the crystallization behavior of polypropylene (PP) during extrusion foam process was investigated under various processing conditions in the absence and presence of supercritical carbon dioxide (scCO2). First of all, the effect of varying the flow rate on PP crystallization was examined without dissolving scCO2 through in-situ visualization. The results suggest that crystallization can be induced in the melt during extrusion with high dependency on the flow rate. A higher mass flow rate leads to higher shear and strain rates; on the other hand, it reduces the residence time in the second extruder and in the die where the polymer is being cooled. In the presence of scCO2, the crystallization kinetics of the polymer melt was altered when compared to the case without any gas. Finally, through the in-situ visualization of the crystals and off-line characterization of the foamed product, the experimental results show that the quality of the foam is governed by the crystal morphology developed before foaming. Keywords: Crystallization, Visualization, Extrusion Foam Process, Polypropylene, Supercritical Carbon Dioxide.