The properties and morphologies of UV-cured epoxy acrylate (EB600) blend films containing hyperbranched polyurethane acrylate (HUA)/hyperbranched polyester (HPE) were investigated. A small amount of HUA added to EB600 improved both the tensile strength and elongation at break without damaging its storage modulus (E'). The highest tensile strength of 31.9 MPa and an elongation at break around two times that of cured pure EB600 were obtained for the EB600-based. film blended with 10% HUA. Its log E' (MPa) value was measured to be 9.48, that is, about 98% of that of the cured EB600 film. The impact strength and critical stress intensity factor (K-1c) of the blends were investigated. A 10 wt % HUA content led to a K-1c value 1.75 times that of the neat EB600 resin, and the impact strength of the EB600/HPE blends increased from 0.84 to 0.95 kJ m(-1) with only 5 wt % HPE addition. The toughening effects of HUA and HPE on EB600 were demonstrated by scanning electron microscopy photographs of the fracture surfaces of films. Moreover, for the toughening mechanism of HPE to EB600, it was suggested that the HPE particles, as a second phase in the cured EB600 film, were deformed in a cold drawing, which was caused by the difference between the elastic moduli of HPE and EB600. (c) 2005 Wiley Periodicals, Inc.