Foaming Behavior and Water Absorption-Desorption Cycle of Polylactide for Food Packaging

Abstract

This study investigates the foaming behavior of polylactide (PLA), notoriously difficult to foam, using a pressure-induced batch foaming method with supercritical carbon dioxide (sc-CO2) as the physical blowing agent. Choosing sc-CO2 has strategic advantages due to its easily controlled critical point and high solubility in PLA, making it convenient for laboratory experiments. This research aims to explore PLA foaming with the primary aim of developing a sustainable alternative to expanded polystyrene (EPS) foams. As a bioplastic derived from renewable resources, PLA offers a promising solution to the pressing environmental concerns associated with EPS. By experimentally investigating the foaming of PLA using sc-CO2, this study aims to contribute to developing eco-friendly and sustainable packaging solutions. Foams were prepared at different foaming pressures ranging from 14,426 kPa to 19,574 kPa with a constant temperature of 443.15 K for 135 minutes. The highest density reduction (90.645%) and superior compressive strength (5.597 MPa) were achieved. FTIR analysis indicates no residual chemical reactions in the foaming process, as seen by the absence of the-CH group vibration (2919 cm⁻¹) in the foamed PLA and the presence of the strong O-H peak (3297 cm⁻¹) only in unfoamed PLA. The water uptake test showed that the PLA foam absorbed around 12% water within the first 15 minutes, which is lower than many other biodegradable foams. It also withstood over 3 cycles of 2-hour water immersions, suggesting its potential for sustainable packaging applications.