A phthalic allyl ester having a hydroxyl group [2-(2-hydroxy-3-allyloxypropanocarbonyl)-allylphthatate (HDAP)l was synthesized by the reaction of phthalic monoallyl ester with allyl glycidyl ether. HDAP was added to a diallyl phthalate resin to a concentration of 30 wt % to improve the adhesive properties. These blends were cured with dicumyl peroxide. The lap shear strength of joints was measured to evaluate the adhesive properties of the modified diallyl phthalate resin to steel and copper. The lap shear strength of the diallyl phthalate resin was increased by modification with HDAP. By modification with HDAP, the lap shear strength to steel increased up to about 2.5 times that of the diallyl phthalate resin. Moreover, the lap shear strength to copper was about 3.0 times larger than that of the diallyl phthalate resin upon the addition of 30 wt % HDAP. These results suggested that the secondary hydroxyl group of HDAP (used as a modifier) formed a hydrogen bond to a hydroxyl group of water existing on the metal surface, and as a result, the adhesive strength to metals such as steel and copper increased. The thermal decomposition temperature of the modified diallyl phthalate resin was almost the same as that of the diallyl phthalate resin; on the other hand, the glass-transition temperature of the modified diallyl phthalate resin decreased with an increasing concentration of HDAP. The electrical properties of the modified diallyl phthalate resin were almost the same as those of the diallyl phthalate resin. On the other hand, water absorption after boiling increased with an increasing concentration of HDAP. This result led to the conclusion that the secondary hydroxyl group of HDAP (used as a modifier) formed a hydrogen bond to water. (c) 2007 Wiley Periodicals, Inc.