Study on the UV curing behavior of tung oil: Mechanism, curing activity and film-forming property

Abstract With the rapid development of industry and the growing shortage of fossil energy, tung oil has attracted much attention of researchers because of its environment-friendly and renewable advantages. In this work, the curing mechanism of tung oil under UV irradiation is studied by the titration of the peroxide value, Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. In addition, the effects of different photoinitiators on the UV curing behavior of tung oil are investigated through monitoring the gel fraction of the cured films. Finally, the morphology and the solvent resistance of the films cured with different condition are estimated by scanning electron microscope and solvent resistance testing. The results display that UV curing of tung oil is composed of oxidative polymerization and free radical polymerization. Among the different photoinitiators, the triarylsulfonium salts at amount of 5 wt% is one of the most efficient ones for the UV curing of tung oil. A novel UV curable system containing tung oil is constructed to supply a reference to expand the application of drying oils.