Development of poly(lactic acid) cellular materials: Physical and morphological characterizations

The present study aims at assessing the extrusion foaming characteristics of two commercial grades of poly(lactic acid) (PLA) using a chemical foaming agent (CFA). For each PLA the process was optimized based on a maximal void fraction criterion. The extruder die temperature significantly affects the void content (maximal for about 195 °C). An increase in the barrel temperature profile was also correlated with an increase in the void fraction. Moreover an increase in CFA concentration increased the PLA void fraction, and in some cases induced a decrease in cell density and an increase in cell size. Finally, an optimal value of 47% void fraction was obtained. Finally, optimally processed PLAs with varying CFA contents were tensile tested. The results pointed out that it was possible to observe significant decrease in the density and increase in some specific mechanical properties by controlling the extrusion foaming process.