A sustainable approach for linen dyeing and finishing with natural lac dye through chitosan bio-mordanting and microwave heating

Sustainability has become a global requirement in all industries. In the textile sector sustainability can be achieved by developing innovative techniques, approaches, and machinery. The current study introduces a sustainable approach for linen dyeing with natural lac dye using microwave heating after the treatment with chitosan as a cationic bio-mordant. The chitosan treatment was carried out by a pad/dry-cure process with citric or acetic acid. Linen samples were characterized by scanning electron microscopy (SEM), and fourier transform infrared spectroscopy (FTIR). The results confirmed the deposition of chitosan on linen fabric with both citric and acetic acid. X-ray diffraction (XRD) was used to determine the change in the crystallinity of linen fabric after chitosan treatment and lac dyeing. The color strength results confirmed the successful application of chitosan as a bio-mordant and the efficiency of microwave heating in shortage the dyeing period in lac dyeing, where the K/S increased from 1.54 to reach 18.86 and 13 with acetic and citric acid, respectively in 7 min. Furthermore, the maximum color strength was achieved at pH 3 of lac dye and the presence of chitosan eliminated the usage of salt in the lac dyeing of linen fabrics. Fastness properties of the lac dyed linen fabrics to wash, light, and perspiration have been discussed. The functional properties (antibacterial activity and UV protection) of linen fabrics were assessed. The antibacterial activity was decreased after the chitosan-treated linen samples were dyed with lac dye. However, the UPF of linen samples was enhanced after lac dyeing.