Sorption and Diffusion of Supercritical Carbon Dioxide into Nitrocellulose with or without Cosolvents

Sorption and diffusion of supercritical carbon dioxide (SC-CO2), SC-CO2 +ethanol, or SC-CO2 + ethyl acetate into nitrocellulose were examined at 40 degrees Cunder 25MPa for the 0.5-6 h soaking duration using a gravimetric method. A small addition of cosolvent into SC-CO2 leads to a dramatic increase in solubility, desorption diffusivity and sorption diffusivity of CO2 into nitrocellulose. The addition of ethyl acetate or ethanol into SC-CO2 boosts the equilibrium solubility of CO2 in nitrocellulose from 15.74 wt% to 23.52 wt% and from 15.74 wt% to 22.72 wt%, respectively. The desorption diffusivities are found to be higher than the sorption diffusivities due to the plasticizing effect of CO2.