Effect of pigment colour on the printing performance of synthetic leather using a ultraviolet-curable water-borne polyurethane acrylate binder

The effect of pigment colours, cyan (C), magenta (M) and yellow (Y), and a blend of these (CMY blend) on the printing performance of synthetic leather using a ultraviolet (UV)-curable water-borne polyurethane acrylate binder and two types of photoinitiators was investigated. The curing process was carried out at different radiation doses using gallium and mercury UV lamps in combination. The performance of the prints was evaluated with abrasion resistance, crock fastness, gloss and hardness values and K/S. Chemical changes in the cured film structures due to UV curing were analysed by Fourier Transform–infrared spectroscopy measurements. The highest hardness values for clear and pigmented cured films were obtained with a gallium and mercury lamp combination at the highest energy density (1529 mJ/cm²). The highest K/S was obtained for the sample printed with the formulation including the C pigment and cured under a gallium and mercury lamp combination at low energy density (398 mJ/cm²). The M-pigmented film displayed the highest hardness and abrasion resistance, whereas lower values were obtained with films pigmented with Y and C, and CMY blend, successively. The highest dry and wet crock values were obtained with the formulation including the M pigment. CMY-pigmented film showed the highest gloss values at all energy densities. The pigment colour affected the curing degree of printed films due to the different absorption/transmission intervals of each colour in the UV spectrum.