Novel curing systems of a urethane/epoxy resin [diglycidyl ether of bisphenol A (DGEBA)] alloy using the moisture-latent hardener ketimine (K-systems) were investigated on the DGEBA-rich side and were compared with aromatic diamine curing systems (A-systems). Almost all the added DGEBA was separated from the polyurethane matrix and dispersed as 2-10-mum-diameter particles after curing in the A-systems. Therefore, DGEBA did not act as a reinforcing agent for the polyurethane matrix. However, 50% of the added DGEBA was dispersed as particles with a diameter of 1-4 mum, and the other 50% was incorporated into the polyurethane matrix in the novel K-systems. Therefore, the polyurethane matrix in the K-systems should be reinforced effectively by both incorporated and finely dispersed DGEBA and should result in significant improvements in the stress-strain properties. (C) 2004 Wiley Periodicals, Inc.