Calculating barrier properties of polymer/clay nanocomposites: Effects of clay layers

We analyzed the effects of clay layers on the barrier properties of polymer/clay nanocomposites containing impermeable and oriented clay layers. Using the relative permeability theory in combination with the detour theory, we obtained new relative permeability expressions that allow us to investigate the relative permeability R_p as a function of lateral separation b, layer thickness w, gallery height H, layer length L, and layer volume fraction Φ_s. It was found that intercalated and/or incomplete exfoliated structures and dispersed tactoids with several layers can effectively enhance the barrier properties of the materials. Furthermore, we developed the chain-segment immobility factor to briefly discuss the chain confinement from clay layers. The results showed that the chain confinement enhanced the barrier properties of the intercalated nanocomposites. Our model is better consistent with the experiments when Φ_s>0.01. The findings provide guidelines for tailoring clay layer length, volume fraction and dispersion for fabricating polymer-clay nanocomposite with the unique barrier properties.