Compostable, Full Biobased Foams Using Environmentally Benign Manufacturing

With initiatives on carbon capture utilization, use of CO2 in the manufacture of foamed polymers is valuable. The low solubility and strong temperature/pressure correlation to utilization remains a limit. Here we explore two aspects of green manufacturing. Use of a biopolymer and CO2 to foam it. Microcellular foams were produced from amorphous polylactic acid (PLA) with 12% d-lactide content using the batch foaming method. The batch method produces foams that are affected by cell nucleation, growth and solidification. In the thermal soak method, CO2 was introduced into PLA above its Tg, depressurized resulting in solidification, followed by soaking in a hot water bath for trapped CO2 to be released. In a second method, CO2 injected above the Tg was held at a temperature above ambient to encourage cell growth followed by a quench. The results showed that foams made through the decompression technique at foaming temperature of 55 °C were rigid in nature and had a better mix of cellular architecture due to their well-defined bimodal cellular structure compared to the foams made at foaming temperature of 75° C. Excellent mechanical and good sound absorption properties were attributed to the bimodal distr. Thermal conductivity values of (0.031–0.063) W/mK obtained for the PLA foams made using the thermal soak and decompression techniques was equivalent to that of petroleum based extruded polystyrene (EPS) and expanded polystyrene (XPS) foams ∼ (0.03–0.06) W/mK valuable for building insulation.