Isosorbide-based high performance UV-curable reactive diluents

Abstract

In UV-curable coatings, a reactive diluent is mainly used to adjust the viscosity of the formula and participates in UV curing. However, it is still a great challenge to obtain a reactive diluent that has good diluting ability and good mechanical properties. In this study, isosorbide di(meth)acrylate (ISD(M)A) was designed and synthesized as a photocurable reactive diluent. The photo-polymerization kinetics of the reactive diluent were studied using real-time infrared spectroscopy. The diluting ability of reactive diluents in polyurethane acrylic (PUA) and epoxy acrylic (EA) were studied using a rheometer. Reactive diluent was mixed with PUA and EA to prepare a series of UV curable coatings, and the thermomechanical properties, mechanical properties, and basic coating properties of these coatings were evaluated. The results show that for both PUA and EA, ISD(M)A exhibits dilution capabilities similar to those of commercially available reactive diluents. The addition of 30 wt% reduces formula viscosity by three orders of magnitude, but the glass transition temperature (Tg) and pencil hardness of the ISDA-CN981 coating are 62.3 °C and 3H, respectively, which are higher than those of HDDA-CN981 (51.9 °C and 2 H). Moreover, the coatings that contain ISD(M)A have a higher storage modulus and good impact properties. In this work, good dilution ability of the active diluent and high mechanical properties of the coating were simultaneously achieved. These bio-renewable, UV-curable isosorbide-based reactive diluents show promise in green photocuring coatings.