The effect of ultraviolet-curable water-borne polyurethane acrylate binder concentration on the printing performance of synthetic leather

In this paper, synthetic leather samples were screen printed with pigmented pastes including two types of photoinitiators and three different concentrations of ultraviolet (UV)-curable water-borne polyurethane acrylate binder. The curing process was conducted under different combinations of lamps (gallium, mercury, gallium/mercury and gallium/gallium/mercury) at three power levels. Abrasion resistance, crock fastness, hardness and colour strength were investigated. Chemical changes in the clear and pigmented film structures because of UV curing were analysed by Fourier Transform-infrared spectroscopy measurements. In hardness measurements, the highest hardness values were obtained with clear and pigmented formulations which have the highest solid content (57%). In colour measurements, higher K/S values were obtained in samples printed with the formulation having a binder concentration of 46%. Wet crock fastness values improved as the energy level increased during curing, and the highest values were obtained with a formulation which had a binder concentration of 57%. Greater amounts of binder in the formulations and increased amounts of energy applied to the surface during curing increased the hardness value of the prints, thus better abrasion resistance was obtained. Overall results suggested that the highest hardness, crock fastness and abrasion resistance values were obtained with the formulation with a binder concentration of 57%. However, for ease of application, printing efficiency and colour strength, the formulation with a binder concentration of 46% is recommended for printing, and curing under consecutive passes with gallium and mercury lamps at 120 W/cm is proposed in terms of energy efficiency and printing performance.