Experimental Determination of Concentration-Dependent Carbon Dioxide Diffusivity in LDPE

摘要

In this work, we experimentally determine the concentration-dependent diffusivity of carbon dioxide in low-density poly(ethylene) (LDPE). For this purpose, experiments are carried out to obtain pressure-decay data for isothermal diffusion of the gas in the polymer. Based on a detailed mass transfer model, variational calculus is used to establish the conditions necessary to yield the concentration-dependent diffusivity that enables the model-predicted mass of absorbed gas in polymer to match with the experimental counterpart. A computational algorithm is implemented to solve the model and the conditions and obtain the diffusivities. Determined at 120 and 130 degrees C for four different pressures in the range 0.352 to 1.232 MPa, the diffusivities are strong unimodal functions of gas concentration in polymer and of the order 10(-9) m(2) s(-1). Mathematical correlations are developed to calculate the diffusivity at a given temperature, pressure, and gas concentration. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 380-387, 2009