A NEW GAS DIFFUSIVITY MEASUREMENT TECHNIQUE FOR CO2 INFUSED POLYMER SYSTEM DURING GAS DESORPTION

摘要

In this study, theoretical CO2 diffusivity coefficients in amorphous polymers were calculated from dielectric constant changes during CO2 desorption. Compared with experimental diffusivity coefficients from a gravimetric method, these values agree well with each other. Three amorphous polymer films made from Polystyrene (PS), Polycarbonate (PC), and Cyclic Olefin Polymer (COP) resins were saturated with supercritical CO2 under high pressure in a pressure chamber. Then, the CO2 infused films were removed from the chamber for gas desorption experiments. Both capacitance and weight changes of the samples were recorded by an Inductance, Capacitance and Resistance (LCR) meter and a scale simultaneously. The dielectric constant changes of the polymer/CO2 systems were calculated from the capacitance change measurements during gas desorption experiments. The trend of dielectric constant changes is found to be similar to that of the CO2 weight percentage changes during gas desorption. A mathematical model was built to predict the CO2 weight percentages at any given time during a desorption process from the measured dielectric constants. The theoretical diffusivity coefficients were obtained from the predicted CO2 weight percentage changes and these theoretical diffusivity coefficients agree well with the experimental data.