Synthesis, characterization, and thermal stability studies of bisphenol-A type novolac epoxy-polyurethane coating systems for in-mould decoration ink applications

Recently, In-mould decoration (IMD) ink has gained considerable attention, which is used for decorating plastic surfaces through IMD craft. In this work, series of hydroxyl terminated bisphenol-A type novolac epoxy resins modified with benzoic acid (BAMEP) were synthesized in the presence of tetramethylammonium bromide catalyst. The chemical structures of the obtained BAMEP were characterized using FTIR, 1H NMR analyses. Epoxy-polyurethane coatings (BAMEP-PUs) were also obtained by curing reaction among BAMEP, cross linker polyisocyanate IL1351 and phthalic anhydride, which is desirable for IMD ink applications. The cured BAMEP-PUs, unmodified bisphenol-A type novolac epoxy resins (EP) and alkyd polyol A450 were determined by thermogravimetric analyzer, and their thermal stability were also compared. The results showed that the obtained BAMEP-PUs had much better thermal stability than the conventional polyurethanes, and the thermal stability of them at different temperature stage depended largely on the content of BAMEP and cross linker IL1351.