Diffusion of CO_2 at elevated pressures through several polymer film samples polyethylene, polystyrene (1-7.5 MPa) and polyvinylchloride (7.5-10 MPa) was studied using in situ technique. Toward this end we were constructed special setup on the base of Millipore Corporation high pressure stainless still filter holder. It was shown that the filtration technique used to monitor the CO_2 diffusion process through polymer films allowed the measuring of diffusion coefficients of carbon dioxide molecules in the polymer samples by analyzing the kinetics of penetration through film free volume. The diffusion coefficients of CO_2 in polymers were calculated by Barrer's method from time delay. Diffusion coefficients obtained by permeability method were located in the good accordance with the one's calculated from the optical boundaries displacement. The diffusion coefficient dependences on pressure and temperature were analyzed. It was shown that diffusion coefficients were increased with rise of temperature and pressure. The experimental data were fitted by computer simulation of the permeation process. Insufficient durability of some polymers after intensive swelling by CO_2 at elevated pressures (near 7.5-10 MPa) was limitative motive to use this method with very thin films (less than 20 micrometers). The influence of CO_2 plasticizing effect on the diffusion process is discussed.
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