Effect of CO ₂ laser treatment on the leather surface morphology and wettability

The aim of this research was to determine the influence of pulsed CO ₂ laser treatment on crust leather surface morphology and wettability. The obtained results revealed that pulsed CO ₂ laser engraving can be used as an effective tool for crust leather surface treatment. Pulsed CO ₂ laser treatment only negligible affects the macrostructure of leather, while the morphology and wetting of the leather surface after treatment were changed. It was found that an increase of laser pulses number increases the initial water contact angle value and intensifies the water droplet relaxation process. After laser treatment, the water droplet contact angle relaxation rate increases twofold compare to those for untreated leather. SEM micrographs showed increased defectiveness with rough surface patterns, thermally affected areas, and change of microstructure. The EDX analysis revealed that the engraved leather surface contains a significantly higher amount of carbon but smaller quantities of oxygen compared to those of untreated samples. It was found that only after laser treatment chromium and sulfur in the EDX spectra appear while for untreated samples these elements on the surface were not observed. The results indicate that for investigated samples laser engraving does not affect the concentration of hexavalent chromium and are in accordance with EU requirements.