The polar PA-6 has high affinity for permeant water molecules, while the nonpolar polyethylene phase and the nanoclay present in the systems studied can act as physical barriers for water vapor permeation.
The barrier resistance of polyethylene, a common polyolefinic packaging material, can be enhanced for nonpolar permeants by blending with a minor phase of nylon 6 (PA6).
Diffusion coefficients for permeant uptake in polyester [D.
1/2] might be expected to exhibit behaviour similar to that of nonlyphenol ethanoate, however its behaviour is closer to that of isopropylmyristate and the initial permeant uptake being slightly faster but the subsequent diffusion is slightly slower, Fig.
The free-volume parameters of several permeants
were published by Hong , in a paper where the author also describes a method to regress these parameters from viscosity data.
The regions through which the permeant molecules must travel are thus reduced.
As superstructure or spherulitic sizes increase, permeant molecules must follow paths of greater tortuosity.
For a flat permeable membrane separating two volumes of gas, the permeant flux J through a uniform section of membrane is given by
When helium, instead of natural gas, is used as the permeant through HDPE or XLPE, the rate of gas flow increases, as one might expect.
Percolation approach leads to analogous formulae for the permeability , elastic modulus [37, 38], and diffusion coefficients (for small permeant
molecules)  of binary blends with negligible contribution of one component to the considered property.
These results prove that the fibrillar morphology perpendicular to the direction of transport of the permeant improves the barrier properties of the material.
Indeed fibrils (L x [Phi]v) are compared with plates (L x L x W, W: third edge parallel to the direction of permeant transport).