Solubility and diffusivity of CO2 in poly(l-lactide)–hydroxyapatite and poly(d,l-lactide-co-glycolide)–hydroxyapatite composite biomaterials

Solubility and diffusivity of supercritical CO2 in poly(l-lactide)-hydroxyapatite (PLLA–HA) and poly(d,l-lactide-co-glycolide)-hydroxyapatite (PLGA–HA) composite materials were measured using a magnetic suspension balance at a temperature of 313 K and a pressures range of 10–30 MPa. The effect of the HA concentration on the solubility and diffusivity was investigated by varying filler content in the range of 0–50 wt%. For the PLLA–HA composites the solubility decreases with the increase of filler concentration. Diffusivity of the gas in the substrate is also lower as the HA content increases. In the case of PLGA–HA composites, small filler content favors the solubility and diffusivity of CO2 due to incomplete wetting of the solid particles by the polymer. As the amount of HA increases solubility decreases. The results suggest that dense CO2 could be used as a ‘green’ processing agent for composite biomaterials when organic solvents or high temperatures should be avoided.