UV-Curable Coatings from Multiarmed Cardanol-Based Acrylate Oligomers

Multiarmed, cardanol-based acrylate oligomers were prepared via the ring-opening reaction between cardanyl glycidyl ether (CGE) and polyacids, followed by epoxidization of the unsaturation in alkyl side chains of cardanol segments, and acrylation of the resulting epoxy groups. Biobased coatings were produced from UV-radiation-initiated curing of these acrylates; the coating properties were then characterized in detail. The acrylate oligomers were fully characterized using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR), and proton nuclear magnetic resonance (H-1 NMR). The UV-curing behavior of these acrylates was determined using real-time IR. The results indicated that the conversion of acrylate unsaturation increased with increasing oligomer functionality. These oligomers were formulated into UV-curable coatings, and the coating properties were evaluated to determine hardness, adhesion, chemical resistance, gloss, and surface properties. The properties of cured thermosets were also studied using tensile testing, dynamic mechanical thermal analysis (DMTA), and thermogravimetric analysis (TGA). Compared to coating from benchmark biobased UV-curable oligomer, acrylated epoxidized soybean oil (ASBO), cardanol-based coatings showed higher hardness, excellent adhesion, and enhanced thermal and mechanical properties while maintaining reasonably high biorenewable contents. These improvements in coating performances can be contributed to their unique oligomer architectures that combined the structural features of rigid benzene ring, long flexible alkyl chains, and polar hydroxyl groups.