Assuming a starch based material can be found able to replace extruded polystyrene foam, a renewable alternative would be available that strongly reduces the amount of foamed plastics in waste streams. In this study it is shown that by the foaming of potato starch based expandable beads such a material can be produced. Expandable beads out of pure potato starch were produced by extrusion compounding. Extrusion conditions and material composition were chosen such as to enable full destructurization of the starch while minimizing degradation. Extrusion yielded totally amorphous expandable beads with a glass transition temperature ranging from 70 to 120°C, depending on the water concentration. In a successive step, the expandable beads were foamed on an injection molding machine. The resulting foam properties depended strongly on the actual processing conditions and on the plasticizer content. A material composition and processing conditions were found that facilitate the processing of potato starch into resilient thermoplastic foams. At a density of 35 kg/m3 and an average cell size of 85 µm, the properties of these foams are comparable to those of extruded polystyrene foam.
KeywordsGlass Transition Temperature Potato Starch Nucleate Agent Native Starch Injection Speed
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