CO2 laser treatment as a clean process for treating denim fabric

• CO2 laser treatment process, was used for colour fading treatment of denim fabrics.
• Two types of denim fabrics were CO2 laser treated.
• Colour fading effect and dimensional stability were evaluated.
• CO2 laser treatment is a clean production process.

In this study, a carbon dioxide (CO2) laser was used for the colour-fading treatment of denim fabrics. Two types of denim fabrics were laser-treated: one was manufactured with low-twist yarn spun by torque-free ring-spinning technology, and the other was manufactured by conventional ring-spun yarn. Commercially available torque-free ring-spun cotton yarn was used to manufacture the denim fabrics. For comparison, one specimen of denim fabric featured torque-free ring-spun yarn in the warp direction and conventional ring-spun yarn in the weft direction, whereas another specimen featured conventional ring-spun yarn in both the warp and weft directions. The warp yarn of both specimens was dyed by the same indigo dyeing process. The denim fabric samples were treated with a CO2 laser under the same conditions, and two laser processing parameters, namely, (i) resolution and (ii) pixel time, were used to adjust the laser power. After laser treatment, the colour properties (reflectance and colour parameters of the fabrics, such as the K/S value (the Kubelka-Munk function was used to represent the colour yield of the fabrics, where K is absorption and S is scattering) and CIE L*a*b* values) and dimensional stability of the denim samples were compared, and the results were analysed thoroughly. In addition, the colour-fading effect induced by CO2 laser treatment was compared with that induced by conventional cellulase treatment. Experimental results revealed that CO2 laser treatment is an effective alternative means of producing the colour-fading effect in denim fabrics if the processing parameters can be carefully controlled.