High performance epoxy-layered silicate nanocomposites

High performance epoxy-layered silicate nanocomposites based on tetra-glycidyl 4,4'-diamino-diphenyl methane (TGDDM) resin cured with 4,4'-diaminodiphenyl sulfone (DDS) have been successfully synthesized. Fluorohectorites modified by means of interlayer cation exchange of sodium cations for protonated dihydro-imidazolines and octadecylamine were used. Fluorohectorite exchanged with 1-methyl-2-norstearyl-3-stearnoacid-amidoethyl-dihydro-imidazolinium ions was immiscible with the epoxy matrix. In contrast, fluorohectorites exchanged with hydroxyethyl-dihydro-imidazolinium (HEODI) and ricinyl-dihydro-imidazolinium ions (RDI) favored the formation of a nanocomposite structure. This is most likely due to the presence of -OH groups in their molecular structure, which has a catalytic effect on the polymerization occurring between the silicate layers. The diffusion of epoxy and curing agent molecules between the silicate layers is also promoted. Microscopy observations revealed that the dispersion of the silicate aggregates on a microscale was proportional to the degree of separation of the silicate layers on a nanoscale. Decreased apparent glass transition temperature was observed in all the nanocomposites. Finally, mechanical property studies showed that epoxy-layered silicate nanocomposite formation could simultaneously improve fracture toughness and Young's modulus, without adversely affecting tensile strength.