Permeation and diffusion models relevant to polymer nanocomposites

4 Permeation and diffusion models relevant to polymer nanocomposites 

As reported by several authors and as proved by our studies on the transport behaviour, nanoeomposites exhibit substantial improvements in gas and vapour permeability. This phenomenon has traditionally been explained by a tortuous path model where the high aspect ratio platelets acts as physical barrier for diffusion of molecules.  

These assumptions maximize the distance that the diffusing molecules must travel and thus define the maximum decrease in permeability that geometrically can be expected for the addition of filler to a polymer. In the same article, Nielsen developed a second model for predicting a change in permeability that can be expected when the permeant is partially soluble in the polymer and when the concentration of sorbed molecules at the filler-polymer interface is different from the concentration in the polymer. He proposed that around each filler particle there is an interfacial layer which shows properties different from the bulk polymer saturated with sorbed molecules. In this case the total permeability is divided into two parts (Equation 11.4)  

3 Model for the path of a diffusing molecule through a polymer filled with square plates. 

Pq and Pi are the permeabihties of liquid through the filled polymer, the unfilled polymer and the interfacial region, j), (j)i, (j p and the volume 

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