Phytic acid-based adhesion promoter for UV-curable coating: High performance, low cost, and eco-friendliness

In this work, aiming to enhancing the adhesion of UV-curable coatings to metal surface, a phytic acid based adhesion promoter with photo-curable group (PA-GMA) was designed and prepared via a ring opening reaction of phytic acid (PA) and glycidyl methacrylate (GMA) in aqueous solution. Via the adjustment of PA/GMA feeding ratios, a series of PA-GMA with different contents of photo-curable methacrylate group have been synthesized. The structure of the bio-based PA-GMA was verified using 1H NMR, FTIR and XPS spectroscopy. The developed PA-GMA could significantly improve the adhesion strength between UV-cured coatings and metal substrates, which was superior to that of commercial phosphate ester adhesion promoters. Accompanied by the significantly enhanced adhesion performance, outstanding corrosion protection properties were also demonstrated. This study offers a novel route to prepare an eco-friendly and low-cost adhesion promoter using natural compound and a new strategy to tackle adhesive failure in UV-curable coatings.