Toughened epoxy hybrid nanocomposites containing both an organophilic layered silicate filler and a compatibilized liquid rubber

Hexahydrophthalic acid anhydride-cured bisphenol A diglycidyl ether (BADGE) was used as matrix material for hybrid nanocomposites containing both inorganic nanofiller and compatibilized polyether liquid rubbers. Compatibility between organophilic fluorohectorite, modified by means of intergallery cation exchange with bis(2-hydroxyethyl)methyldodecylammonium, and the liquid rubber triol was achieved by partial transesterification of the polyether end groups with methyl stearate to incorporate stearate end groups. Thermal analysis, dynamic mechanical analysis, mechanical testing, wide-angle X-ray scattering, and transmission electron microscopy were used to measure thermal, mechanical, and morphological properties of the hybrid nanocomposites. Without compatibilization, the rubber does not phase separate and flexibilizes the epoxy resin. Toughness is enhanced at the expense of stiffness, strength, and glass temperature. The stearate compatibilizer is sufficient to achieve phase separation of the rubber. This compatibility matching represents the key to novel phase-separated nanocomposites with significantly improved toughness and only marginally lower stiffness.