Synthesis and properties of UV-curable acrylate functionalized tung oil based resins via Diels-Alder reaction

Tung oil-inspired UV-curable resins for coating materials were synthesized by Diels-Alder reaction between tung oil and maleic anhydride (MA), then subsequent reaction with 2-hydroxyethyl acrylate (HEA) or pentaerythritol triacrylate (PETA), and final modification with glycidyl methacrylate (GMA). Structures of the obtained resins designated as HG-MAT and PG-MAT mainly depend on feeding ratio of MA, tung oil, and HEA (or PETA). Results of both 1H NMR and FTIR revealed that the targeted resins were successfully prepared. The resins had broad molecular weight distributions with PDI from 1.70 to 2.20 due to the complicated side reactions. UV-curing kinetics of the resins was studied by Photo-DSC, and thermal properties of their cured films were investigated by DSC and TGA. Higher content of acrylate CC bonds led to faster curing rate but lower conversion of CC bond. The cured films had a glass transitions in the range of 40-52 °C. All the cured films possessed excellent thermal stability, and the start temperature of decomposition (Tsta) was above 350 °C.