Abstract for presentation at Chemeca 2007

The understanding of gas uptake behaviour of a polymer is important for many different applications such as for the industrially important production of ultra low density microcellular & nanocellular foams. Currently Simha -Smocynsky (1976) and Sanchez – Lacombe (1969) theory have been found to be reasonably effective for predicting solubilities for polymeric nanocomposites. The basic assumption of random mixing within the lattice in these theories is not applicable for these nanocomposites. Hence these lattice based models have been modified for the case of non random mixing by using the Guggenheims quasi chemical approach and the contact fraction approach in calculation of configurational entropy within the lattice. Additionally the model also takes into account possible particle to particle interaction. The model is effective in explaining the effect of dispersion, size, interaction potential and the amount of clay loading on solubility thus providing a more comprehensive approach for prediction of solubility of gases in polymer nanocomposites. The experimental determination of solubility was carried out by conducting saturation experiments in a batch setup using Polypropylene/clay nanocomposites with supercritical CO2 under different pressures (up to 2500 psig) & temperatures (up to 150C). The above model has been verified experimentally and a good agreement between the theory and experiment has been found. A probable theoretical mechanism is proposed to explain the simulation results at each stage. It has been found that the segmental free length is not affected but the repulsion and the free volume is affected with clay loading affecting solubility and diffusivity.