We report mechanical and thermal characteristics of a network composed of poly(propylene oxide) (PPG) and poly(butyl acrylate) crosslinked with tolylene diisocyanate. It was found that addition of about 4 wt % of an epoxy resin resulted in a higher mechanical toughness and less discoloration. Furthermore, it was found that the epoxy has a self-restoration function against thermal degradation of the network. The reaction mechanism between the network and the epoxy was investigated with infrared spectroscopy and C-13-NMR and the effect of the epoxy resin on the thermal stability and physical properties is discussed.