Abstract
Interfacial structural changes of UV cured urethane acrylate coating films were investigated using ATR FTIR spectroscopy. These studies show that at the film–air (F–A) interface, when photo-initiator levels do not exceed 0.1% w/w, the band area ratio of H-bonding to non-H-bonding carbonyl stretching vibrations is proportional to UV energy density. However, when the initiator level is increased to 5% w/w, an increase of up to 200 mJ/cm 2 UV power is required in order to achieve a similar band ratio, and at higher photo-initiator levels, the amount of energy levels off. Analysis of the H-bonded to non-H-bonded band ratio near the film–substrate (F–S) interface shows that the band area ratio increases further away from the interface. At shallower depths, around 0.84 μm from the F–S interface, the magnitude of the H-bonding/non-H-bonding is smaller than that observed for the same penetration depths before UV exposure for lower photo-initiator concentration or lower energy UV exposure.
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