Study of intercalation and exfoliation processes in polymer nanocomposites

The physics of both intercalation and exfoliation processes are discussed and the conditions that lead to a higher level of clay exfoliation in flexible polymer matrixes are examined. The process of exfoliation involves not only mechanical stresses but also diffusion phenomena, with a diffusion coefficient that varies as the inverse of viscosity. To examine the mechanism of exfoliation, mixtures of 80 wt % of poly(ethylene-co-1-octene), 15 wt % of ethylene-octene maleic anhydride grafted with 0.2-0.5 wt % maleic anhydride, and 5 wt % of Cloisite 30B were prepared by mixing them in solid state. To examine the effect of clay exfoliation level on the modulus of the nanocomposites, various samples were prepared with different levels of exfoliation. The results show that the best level of exfoliation requires medium matrix viscosity. This is dictated by a balance between mechanical stresses that necessitate a high level of viscosity and a diffusion process that requires rather low medium viscosity.