Extraction of Natural Dyes from Polygonum odoratum Lour as an Alternative Dyeing for Thai Silk Using Different Metal Salt Mordants

Polygonum odoratum Lour (P. odoratum) is one of the economic indigenous plants, produced annually in huge amounts. Thus, seeking alternate applications for P. odoratum, such as use as a natural dye source, is one of the strategies for reducing market oversupply. The objectives of this research were to study the optimum conditions for natural dye extraction from P. odoratum and to investigate the effect of different metal salt mordants and adding sequence mordant methods in the dyeing silk process. The mordants used were KAl(SO4), CuSO4, and FeSO4 and the adding sequence mordants were pre-, meta-, and post-mordant techniques. When the extracted dyes and measured by UV-Vis spectroscopy, the results showed that the major extracted compounds were rutin, isoquercetin, and quercetin in ethanol solvent. The most suitable dye extraction condition was 15.0 g of P. odoratum powder refluxed in a solvent of 95% ethanol at 80 & DEG;C for 60 min providing the strongest UV-Vis absorption intensity. In terms of the dyeing process, the effect of adding sequence mordant strategies was a stronger influence on color strength and fastness washing property than that of the different mordants used. The meta-mordanting technique was the most promising strategy because it gave stronger color strength, shortest dyeing time, and good fastness properties to the other methods. Overall, this result confirmed that the extracted dyes from P. odoratum as alternative dyeing for Thai silk were a foreshadowing strategy with the meta-mordanting technique.