Description:
<jats:title>Abstract</jats:title><jats:p>A critical survey of the literature has been made relative to the permeation of water vapor through films of polyethylene. For conventional polyethylene, reported values of permeability range from 0.015 to 0.074 gm. mm./m.<jats:sup>2</jats:sup> day cm. Hg at 25°C. Reported activation energies range from 6,590 to 14,540 cal./mole°C. It appears that the highest activation energies are associated with the lowest permeability coefficients. Recent investigations of the permeability of intermediate and high‐density polyethylenes are not in agreement with one another The explanation is offered that part of the transport of water vapor through these materials occurs by Fickian diffusion through the amorphous fraction of the polymer and part occurs by passage through micropores in the polymer film. The expectation exists that a superior water‐vapor barrier could be developed using ultralinear, crystalline polyethylene of high molecular weight. However, an incisive experimental test of this supposition would first have to be concerned with a more complete characterization of polyethylene in the solid state than has heretofore been employed in diffusion and permeability studies.</jats:p>