Dissolution And Diffusion Of Supercritical Carbon Dioxide In Nitrocellulose Research

Aiming at solution performance of supercritical carbon dioxide (SC-CO2) and cosolvent (ethyl acetate, acetone and ethanol) to nitrocellulose, this paper not only studys solution and diffusion of SC-CO2into nitrocellulose, but researchs the influence and mechanism of cosolvent on the solubility and diffusion coefficient. A gravimetric method was used to study the solubility of SC-CO2into nitrocellulose, the Fick’s diffusion model was applied to estimate the diffusion coefficient. The FTIR spectra is used to analysis changes of feature group peak in the diagram and show the reason of solution and diffusion of SC-CO2and SC-CO2+cosolvent in nitrocellulose, the group is belong to CO2, nitrocellulose and colovent in nitrocellulose/SC-CO2/colovent homogeneous system.The solubility of CO2in nitrocellulose increases with solution time until the equilibrium reaches. Temperature seems more significant in affecting the equilibrium time, which comes quick at high temperature, while Pressure does not lead to a distinctly difference on the saturated time; The solubility increased with temperature increasing and showed an inverse trend with pressure increasing; The diffusivities values in solution increase with increasing temperature and are of no distinct trend to a variety of pressures; The values of desorption diffusivities are only ralated to the amount of CO2inside the polymer specimens, which has nothing to do with temperature and pressure. A small addition of cosolvent (ethyl acetate, acetone and ethanol) into SC-CO2leads to a dramatic increase in solubility of CO2into nitrocellulose; Solubility increase depends largely on the plasticizing effect for cosolvent, and as a function of cosolvent percentage, the equilibrium solubility of CO2into nitrocellulose exhibited a maximum. The FTIR spectra show that there is the different interaction in COi, nitrate ester group and cosolvent, and cosolvent greatly affect characteristic peak of nitrate ester group, and the influence degree is related to the plasticizing effect for cosolvent.The results of the study in this paper would be the preliminary theoretical base for studying microporous foaming of propellant according to SC-CO2.