Toughening of silane modified bis‐phenol‐A epoxides

The fracture toughness of two alkoxysilane modified bis-phenol-A (BPA) epoxides were compared at three different temperatures. Organosilanes were utilized to synthesize the modified epoxides; 3-aminopropyl triethoxysilane reacted with the telechelic oxirane (aminosilane functionalized epoxide, ASE); and 3-(triethoxysilyl) propyl isocyanate reacted with the secondary hydroxyl group of the repeat unit (isocyanatesilane functionalized epoxide, ISE). Pre-hydrolyzed and condensed tetraethyl orthosilicate (TEOS oligomers) and TiO2 were added to modified epoxides along with an amine hardener. The films were evaluated using DSC, TGA, tensile, and fracture toughness. During film formation, there were two competing chemical pathways: one based on in situ inorganic reactions of silanes and silicates, and the other based on organic reaction of amine crosslinker with epoxide groups. The aminosilane modified epoxides (ASE) indicated higher compatibility with TEOS oligomers or TEOS oligomers/TiO2 than the isocyanate-silane modified epoxides as smaller agglomerates observed with AFM and SEM images. Theses interactions made ASE tougher, as there was an improvement in the fracture toughness, tensile modulus, and impact strength. This study found that the toughness varied at different temperatures (−50, 20, and 60°C).