The effects of promoter and curing process on exfoliation behavior of epoxy/clay nanocomposites

The effects of a catalyst and coupling agent as well as a curing process on exfoliation behavior of CH3(CH2)(15)NH3+-montmorillonite clay in an anhydr ide-cured epoxy-clay system have been investigated by XRD, DSC, and TEM. Th e results have shown that the organoclay is easily intercalated by the epox y precursor during the mixing process, and the clay galleries continue to e xpand during the curing process, but; the Na+-montmorillonite clay is not i ntercalated during either the mixing or the curing process. The results als o suggest that in the cured system without any promoter although partial ex foliated clay layers have already formed, an amount of the intercalation st ructure still remains. Although addition of a promoter or coupling agent in to the cured system significantly lowers the maximum reaction temperature, and during the curing process the layered organoclay can be gradually broke n into nanoscale structures, in which no d(001) diffraction peaks are obser ved, the complete exfoliation is achieved at gel time or before. The possib le mechanism for the complete exfoliation is discussed on the thermodynamic and kinetic point of view. (C) 2000 John Wiley & Sons, Inc.