Solubility of carbon dioxide in a natural biodegradable polymer: Determination of diffusion coefficients

Carbon dioxide solubility in a natural biodegradable polymer, namely poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and the diffusion coefficients are reported. Equilibrium solubility of dense carbon dioxide in PHBV was studied by a gravimetric method in a temperature range from 308 to 313 K and a pressure range from 10.0 to 15.0 MPa. The copolymer presented Fickian behavior and Fick's diffusion model was applied to determine the amount of carbon dioxide present in the samples after a predermined exposure time as well as the diffusion coefficients. Diffusion coefficients for the sorption under supercritical (sc) conditions and desorption at ambient conditions were determined and compared. To evaluate the influence of the HV content in the amount of maximum sorption degree of the polymer, different samples of PHBV copolymers were tested and the sorption curves are here presented.