New age of polymer nanocomposites containing dispersed high-aspect-ratio silicate nanolayers

A new natural mica/epoxy nanocomposite was formed through the exfoliation of a mica layer. The natural mica used was a potassium sericite (K-SE) whose interlayer was saturated with potassium cations. Powdered samples were separated through an air classifier into D-50 = 13.6 mu m (its median particle diameter), D-10 = 7.9 mu m, and D-90 = 23.7 mu m. An organophilic SE was prepared by an ion exchange reaction between the SE powder and alkylammonium solutions of various initial concentrations. As a typical procedure to forming a completely organically modified sample, the K-SE powder was treated with the highest alkylammonium concentration. This corresponded to an alkylammonium (+)/K+ mole ratio = 10.0 which was kept at 90 degrees C for four days. The nanocomposites were prepared by dispersing the organophilic SE in an epoxy resin (diglyxidyl ether of bisphenol A, DGEBA) with subsequent curing in the presence of nadic methyl anhydride (NMA) and benzyldimethylamine (BDMA) at 120-180 degrees C. Considerable exfoliation of the organically modified SE was achieved at a curing temperature of 180 degrees C. The morphology of the nanocomposite showed silicate nanolayers with extremely high aspect ratios that are at levels several dozens to hundreds of times greater than that of conventional exfoliated clay-polymer nanocomposites.