Bisphenol A Diglycidyl Ether-Based Epoxy Networks with Enhanced Storage Moduli Using Silica Nanoparticles Coated by NH2-Functionalized Poly(tetramethylene oxide)

Abstract

Isocyanate-capped chains of poly(teramethylene oxide) (PTMO) are synthesized by the reaction of hexamethylene diisocyanate and polytetramethylene glycol in 2 : 1 molar ratio. Then, the resulting telechelic macrochains are covalently grafted to silica nanoparticles via formation of urethane linkages. Amine-functionalized silica nanoparticles coated by soft and flexible shell of poly(teramethylene oxide) are obtained after hydrolysis of the remaining isocyanate end groups. These organo-silica nanoparticles are homogeneously loaded into diglycidyl ether of bisphenol A epoxy resin in two different contents, i.e. 5 and 10 wt %. Alongside isophorone diamine as the main hardener of the resin, amine groups of the poly(teramethylene oxide)-grafted nanoparticles allow them to participate effectively in the hardening process. The resulting epoxy/silica nanocomposites are thoroughly characterized by field emission-scanning electron microscopy, fourier transform infrared spectroscopy, and X-ray diffraction. Dynamic mechanical thermal analysis showed that the filler considerably enhances storage moduli of the resulting nanocomposites. However, probing the thermal properties of the epoxy/silica nanocomposites by thermogravimetric analysis and differential thermal analysis showed that the filler has no significant effect on the heat stabilities and thermal phase transitions.