Sustainable dyeing of silk with curled dock (Rumex crispus) extract for trace element removal, ultraviolet protection, antimicrobial and anti-oxidant activity

Abstract

This study investigated the dyeability and functionality of silk dyed with curled dock leaf extract. The effects of sugar content and turbidity in the extracted dye solution on dyeing were analysed, along with K/S values and colour fastness, under varying temperatures and times. The metal adsorption of copper ions was examined using inductively coupled plasma. Additionally, the antimicrobial activity, anti-oxidant activity and ultraviolet (UV) protection abilities were tested. Results indicated that sugar content in the dye solution slightly increased after dyeing, while turbidity slightly decreased. The optimal dyeing conditions were confirmed to be 90°C for 80 minutes. The brightness L* was lowered from 92.9 to 74.1, the colour difference ΔE was significantly different at 24.42 and the K/S value increased significantly from 0.2 to 11.7. The overall fastness to washing, perspiration and rubbing was excellent at grade 4 or higher. The UV-A and UV-B protection rates significantly improved from 66.9% and 67.7% to 92.7% and 94.7%, respectively. Anti-oxidant activity, measured by 2,2-diphenyl-1-picryl hydrazyl radical scavenging ability, increased ca. threefold from 34% to 92%. Moreover, the antimicrobial activity was slightly improved from 91.1% and 86.3% to 96.2% and 98% for Gram-positive and Gram-negative, respectively.