Acrylated tannic acid as bio-based adhesion promoter for EB-curable coatings

Electron beam (EB) curing has emerged as a highly attractive technology for advanced coating systems due to its solvent-free nature, energy efficiency, and ability to initiate polymerization without photoinitiators. This feature minimizes extractable species, a critical advantage for environmental sustainability and food safety. This study investigates partially acrylated tannic acid derivatives (TA–GMx) as bio-based adhesion promoters for EB-curable acrylic coatings in metal packaging applications. Tannic acid was functionalized with glycidyl methacrylate to tailor its polarity and introduce polymerizable groups capable of directly participating in EB-induced crosslinking. The resulting TA–GMx additives, synthesized with varying degrees of acrylation x, were incorporated into an industrial, partially bio-based formulation at different loadings (1.0 and 3.0 wt%). Their influence on network formation and interfacial performance was systematically evaluated. Mechanical and electrochemical tests on various metal substrates demonstrated that the incorporation of TA–GMx additives significantly improved adhesion, flexibility under deformation, and resistance to corrosion-induced delamination. Optimal performance was achieved at 1.0 wt% additive concentrations, where a balance between crosslink density and interfacial interactions was established. These findings highlight the synergy between EB technology and bio-based adhesion promoters as an effective strategy for developing high-performance, sustainable coatings for food metal packaging