Redox and photoinitiated crosslinking polymerization

Acrylate-functionalized resins, typically utilized as UV-curable coatings, have been thermally cured by using a cerium salt as redox initiator, to achieve an effective hardening of the non-illuminated areas. The acrylate photopolymerization and redox polymerization were followed quantitatively by hardness measurements, infrared spectroscopy and attenuated total reflectance IR spectroscopy. The redox acrylate polymerization, performed at temperatures of 120-140 °C, was shown to be efficient enough to ensure a satisfying hardening of the shadow areas within minutes. The chemical structure of the acrylate-functionalized oligomer was shown to play a key role on the efficiency of the redox polymerization, urethane-acrylates being more reactive than hydroxylated acrylates. Almost similar mechanical properties were obtained whether the coating was UV-cured or thermally cured. This combination of UV and redox polymerizations proved to be also effective to cure thick pigmented specimens.