Hybrid model for the diffusion of simple and complex penetrants in polymers

A hybrid model, which combines the characteristic features of the Pace–Datyner molecular model with those of the Kulkarni–Stern free‐volume model, was developed to assess the effect of temperature, penetrant concentration, and polymer crystallinity on penetrant diffusivity. The predictive capabilities of the proposed model were tested by a direct comparison with experimental data. The diffusivity of ethylene and propylene vapors in semicrystalline polyethylene and isotactic polypropylene was experimentally measured using a magnetic suspension microbalance. Sorption kinetic measurements were carried out at temperatures up to 80°C and pressures up to 80 atm. The diffusivity was found to increase with temperature and penetrant concentration. Apparently, there was a very good agreement between the theoretical values predicted by the new hybrid diffusion model and the experimentally determined diffusivities. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007