Fine dispersion and property differentiation of nanoscale silicate platelets and spheres in epoxy nanocomposites

Silica spheres (with an averaged diameter of 10nm) and silicate platelets (approximately 100 x 100 x 1 nm(3) in dimension) were allowed to disperse in polyoxypropylene-triamine (400 g/mol molecular weight), then cured with the epoxy resin diglycidyl ether of bisphenol-A (DGEBA). With 1-5 wt% loading of these inorganic silicates, the Cured epoxies exhibited high hardness, transparency, and a low thermal expansion coefficient. These silicate platelets also enhance the epoxy hardness from the pristine 2H to 4H while adding only 0.5 wt%. By comparison, if the spherical silica is used, a similar hardness can only be achieved by loading as high as 5 wt% of the silica. The high aspect-ratio and fine dispersion of the platelet silicates were found to be important factors in influencing the Cured epoxy's properties. In addition, a TEM micrograph shows that the silicate platelets are well-dispersed and have a unique self-arranged lamellar orientation.