Eco-friendly Grafting of Chitosan as a Biopolymer onto Wool Fabrics Using Horseradish Peroxidase

Chitosan and enzymes have been extensively used in modification of wool, due to their non-toxic and eco-friendly characteristics, as well as to reduce pollution in textile production. In the present work, chitosan was grafted onto wool fabrics using horseradish peroxidase (HRP) in order to endow wool with outstanding properties. The reaction mechanism, grafting percentage, and properties of chitosan-grafted pretreated wool fabric including wettability, dyeability, shrink resistance, and antibacterial activity were studied. P-hydroxyphenylacetamide (PHAD), as a model compound for tyrosine residues in wool, was used to study the mechanism of HRP-mediated grafting of chitosan onto wool. UV and FTIR analyses indicated that quinones, which are intermediate of HRP/HO-catalyzed PHAD, reacted with the amino groups of chitosan by Schiff base or Michael addition reactions. Scanning electron microscopy (SEM) showed that dichloroisocyanuric acid pretreatment had an etching effect and some substances were deposited onto the wool fiber. SEM and Fourier transform infrared (FTIR) spectroscopy further confirmed the covalent grafting of chitosan onto wool. Compared with chitosan-grafted unpretreated wool, there was an obvious improvement in grafting efficiency of chitosan onto wool fabric, physical and mechanical properties after pretreatment and chitosan grafting on the wool. For chitosan-grafted pretreated wool fabrics, there was no observable change in the thermal behavior, while the hydrophilicity, dyeability, shrinkage resistance, and antibacterial activity were remarkably improved compared to that of untreated wool. The present work offers a new ecologically acceptable process of grafting chitosan on the wool.