Electron beam-cured linseed oil - Diacrylate blends as a green alternative to overprint varnishes: Monitoring curing efficiency and surface coating properties

Abstract

Electron beam (EB)-cured unsaturated vegetable oil and diacrylate was formulated as an alternative and green overprint varnish (OPV) for coatings in a finishing process. Linseed oil (LO) was applied with tripropylene glycol diacrylate (TPGDA) in different ratios to obtain EB-curable LO-based OPV (eLOPV). The eLOPV were irradiated by EB for curing using various absorbed doses of 10–100 kGy. Change of the functional groups, chemical structure and transition temperature of EB-cured eLOPV were characterized by FTIR, 13C-NMR and DSC. The curing efficacy was assessed by measuring conversion, gel fraction, swelling degree and by characterizing surface properties using solvent rub-test and cross-cut tape test methods. The EB-cured eLOPV exhibited great surface adhesion on substrates. The surface morphologies of the EB-cured eLOPV on papers and plywood sheets were observed by SEM. The results indicate that the eLOPV (LO-TPGDA blend 40: 60 w/w) was completely cured using EB at 30 kGy. Th optical properties were observed via yellowness and whiteness indexes according to ASTM E 313. Color difference and gloss value were measured using colorimeter and gloss meter, respectively. The eLOPV provide good surface qualities, i.e, good surface adhesion, low yellowness, homogeneous cured surface, high gloss value, and hydrophobic surface. Aiming at well-optimized formula and effective EB-curing process, the synthetic chemical can be reduced at least 50% w/w by using vegetable oil without photo-initiator. The utilization of LO and EB curing technology is a promising strategy for bio-/green-coatings approach.