The effect of anhydride categories on the properties of UV-curable epoxy acrylic resin

UV-curable epoxy acrylic resin (EA) has been widely used due to its high hardness, good thermal stability, and low cost. However, EA has some disadvantages including poor flexibility and low impact resistance, which limit the application field of EA resin. Herein, the modified EA resin (REA) was synthesized by modifying bisphenol A epoxy resin (E51) with esterification products of cyclic anhydride (RAH) and 2-hydroxyethyl acrylate (HEA). The effects of anhydride categories on REA properties including mechanical properties, thermostability, gel content, and comprehensive properties were studied. It was found that UV-cured REA resin formed by the anhydride carrying benzene ring or C=C double bond exhibited high gel contents, high tensile stresses (40 MPa), high pencil hardness (H), and excellent water resistance. As the carbon chain of the anhydride increased, the viscosity of the modified resin product decreased sharply, the elongation at break and the thermal stability of the cured resin were improved, and the flexibility and the impact resistance of the cured film were enhanced. In order to combine the advantages of a flexible long chain and rigid benzene ring, REA was modified by chemical blending of glutaric anhydride (GAH) and phthalic anhydride (PAH). When the GAH/PAH molar ratio was 0.3:0.7, the UV-cured film exhibited better impact resistance (35 cm·kg) and flexibility (1 mm) compared with EA, as well as excellent water resistance and ethanol resistance. The results provide theoretical guidance for the design and synthesis of high-performance UV-curable resins.