Reverse exfoliation in a polymer nanocomposite by blending with a miscible polymer

An investigation of the permeability to methanol of blends of a PA-6 nanocomposite and ethylene-vinyl alcohol copolymers (EVOH), containing approximately 32 mol% ethylene, has been conducted. Blends were prepared by melt compounding and permeation measurements were performed by gravimetric uptake methods. The nanocomposite polyamide exhibited significantly reduced permeability compared to the unmodified polymer. The blends exhibited permeability that was non-linear with blend composition. The nanoscale filler in a blend containing up to 50 wt% EVOH remained fully exfoliated, however, in a blend containing 75 wt% of EVOH there was little or no exfoliation and the blend had a measured permeability lower than that of either of the pure components. Electron microscopy and X-ray analysis has indicated a reversal of exfoliation of the nanocomposite filler particles to be responsible.