In this work the cure behavior and rheological and mechanical interfacial properties of the diglycidylether of bisphenol A (DGEBA)/polyurethane (PU) blend system, initiated by 1 wt % N-benzylpyrazinium hexafluoroantimonate as a latent thermal catalyst, were investigated. To characterize the mechanical interfacial properties of the system, the critical stress intensity factor (K-IC) was calculated with a single-edge-notched beam (SEN) beam fracture toughness test. And an impact test was performed at room and cryogenic temperatures to determine the performance of PU at room and low-temperatures, respectively. As a result, the E-c of the blend system was increased with increasing PU content, showing a maximum value at 30 wt % PU, which was in good agreement with the mechanical properties of the blend system. Consequently, these results could be explained by the improvement that occurred in intermolecular hydrogen bonding between the hydroxyl group in EP and the isocyanate group in PU, resulting in increased compatibility of the components within the interpenetrating polymer networks. (C) 2004 Wiley Periodicals, Inc.