Facile synthesis and characterization of renewable dimer acid-based urethane acrylate oligomer and its utilization in UV-curable coatings

A UV-curable polyurethane acrylate (PUA) oligomer was prepared from dimer acid (DA) based polyester polyol (DAPEP) with a monofunctional acrylate precursor which was developed upon isophorone diisocyanate (IPDI) reacted with 2-hydroxyethyl methacrylate (HEMA). The structural elucidation of synthesized dimer acid based PUA (DAPUA) oligomer was verified through Fourier-transform infrared spectroscopy (FT-IR) and Proton nuclear magnetic resonance (H-1 NMR). A series of UV cured coatings were prepared by adding trimethylolpropane triacrylate (TMPTA) and 1,6-hexanediol diacrylate (HDDA) reactive diluents in varying percentages (10-30 wt %) to PUA oligomer. The bio-coatings exhibited exceptional results, including the highest thermal degradation temperature of 382-422 degrees C, glass transition temperature (T-g) of 56.38-66.27 degrees C, the tensile strength of 17.3-30.6 MPa, volume shrinkage of 6.19-9.13 %, and surface roughness of 4.89-28.21 nm. Compared to vegetable oil based UV-curable coatings, long chain dimer acid based PUA oligomer coatings exhibited excellent flexibility, impact, hydrophobicity, and resistance to volume shrinkage.