Dyeing of Silk with Natural Lac Dye from Laccifer lacca Kerr. and Evaluation of Antibacterial and UV-Protective Properties

Insect-based colorants have been utilized for textile dyeing since antiquity due to their color variation and easy availability. In the past few years, the ancient sources of colorants have gained both academic and industrial importance due to the increasing global interest in environmentally friendly and safe products. The lac dye, extracted from lac insect (Laccifer lacca Kerr.), is the main object of this study, focusing on its efficacy in coloration and antibacterial and ultraviolet (UV)-protective functionalization of silk. The anthraquinone components of the dye extract were clarified using Fourier transform infrared spectroscopy (FTIR) and UV–visible spectroscopy (UV–Vis). Besides, the highest color yield of the dye extract was obtained with a material to liquor ratio of 1:10, extraction time of 120 min, extraction temperature of 80 ℃, and pH 7. For the further enhancement of the dyeability of silk, chitosan biopolymer was used as a natural mordant, while alum and copper were used as metallic mordants in the dyeing process. Experimental results indicated that the dyed silk samples had good fastness against washing, rubbing, and lighting. Furthermore, the mordanted–dyed silk presented remarkable bacterial inhibition up to 91.90 and 71.94% against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), respectively, as well as excellent UV-protective properties with UV blockage percentages up to 99.2 and 99.6% for UV-A and UV-B rays, individually. The findings of this study specified the potential of an insect-based colorant as a functional textile dye to replace synthetic dyes and chemical agents.