Determination of Effective Diffusion Coefficients of Nitrogen in Extruded Polystyrene Foam by Gravimetric Sorption

Abstract

A macrogravimctric sorption technique has been employed to obtain time-dependent weight gain data for thin-sliced closed-cell extruded polystyrene foam samples Effective diffusion thickness and diffusion time were used to compute a scaled age parameter The weighing apparatus operated in an isolated chamber filled with pure nitrogen gas The effective diffusion coefficient of the gas in the foam structure was computed from the slope of the weight ratio, defined as the instan tancous weight gain to equilibrium weight gain, with the thickness-scaled age pa ramctcr. Effective solubility coefficient was computed from the film solubility coeffi cicnt, foam to polymer ratio and environmental conditions. The Geometric Factor, computed from the ratio of effective to film permeability, was about four times the value based on cellular dimensions