Estimation of the effective permeability of thin surface layers created by exposure of polyethylene to fluorine

The significantly improved barrier properties of polyethylene, that, result from surface treatment with small amounts of fluorine are explained in terms of the reduced permeability of a thin layer produced by such treatments. Several approaches for correlating the permeabilities of the treated and untreated polymer layers to various penetrants are discussed. An analysis is also presented that permits estimation of the treatment depth corresponding to a given loss rate is related explicitly to the relative permeabilities of the penetrant in the treated and untreated polymer regions.