| The foaming of two biodegradable polymers, PLA and PCL, utilizing a physical blowing agent was investigated. Processing and foaming of the samples was done in an intermeshing counter rotating twin screw extruder with direct injection of the physical blowing agent into the melt through an injection port on the barrel of the extruder. Two gases were used as blowing agents, carbon dioxide, and nitrogen. Two biodegradable polymers polylacticacid (PLA), and polycaprolactone (PCL) and two reference polypropylene, and polystyrene were used in the study.; Several processing parameters such as screw configuration, gas pressure, melt temperature, and cooling methods, were varied to determine the effect on the foam properties. The results indicate that a reduction of 25% in density was achieved. The results also show that in this extrusion process, that carbon dioxide which is more compatible with these biodegradable polymers, was less efficient as a blowing agent than an incompatible gas (nitrogen). |
