Transport of carbon dioxide in linear low-density polyethylene determined by permeation measurements and NMR spectroscopy

This work reports the transport of carbon dioxide in compression molded linear low-density polyethylene films. A common characteristic of the transport is that the curves that depict the dependence of the permeability coefficient of CO2 on the upstream pressure exhibit a sharp increase in the low pressure region as the upstream pressure decreases at moderately high temperatures. This behavior can be explained by assuming that absorption and adsorption processes govern the transport of CO2 in the films. The dual mode parameters calculated for co-extruded and compressed films are compared. The diffusion coefficient of CO2 in the films is also obtained using NMR techniques. The value of the diffusion coefficient is nearly one order of magnitude higher than that determined from permeation measurements. The possible reasons for this discrepancy are discussed.