Solvent Free Generation of Open and Skinless Foam in Poly(l-lactic acid)/Poly(d,l-lactic acid) Blends Using Carbon Dioxide

Abstract

Foams generated via carbon dioxide (CO2) processing typically exhibit a solid skin layer on the exterior surface and a closed-pore structure with limited interconnectivity in the core section thus limiting its application for biomedical intent. By controlling the properties of poly(l-lactic acid)/poly(d,l-lactic acid) (PLLA/PDLLA) blends and using CO2 with specific processing parameters, skinless foams with interconnected porous structure were prepared in this work using only CO2 as a physical foaming agent, which overcome the necessity to use organic solvents and solid porogens. The crystallization behaviors and sorption kinetics of PLLA and its blends were studied. Addition of PDLLA reduces the crystallinity of PLLA/PDLLA blends while treated with CO2 as compared to neat PLLA. The solubility and diffusion coefficients of CO2 in PLLA and its blends were found to be similar. Furthermore, the effect of PLLA/PDLLA blend ratio and CO2 treatment conditions on the foam morphologies was investigated. Through fi...