Studies on dyeing with natural dye Juglone (5-hydroxy-1,4-naphthoquinone)

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:calibri;mso-bidi-theme-font:minor-latin;="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Five fibrous substrates, viz. wool, human hair, silk, nylon and polyester, were dyed till equilibrium with Juglone (5-hydroxy-1, 4-naphthoquinone), a natural dye obtained from the hulls of raw walnut, and the kinetics and thermodynamics of dyeing were studied. The isotherms obtained for all the fibres were linear, indicating a partition mechanism of dyeing. The slope of isotherms increased with the increasing temperature in all the cases except wool, where it was independent of temperature. The standard affinity of Juglone for hydrophobic fibres was higher than that for hydrophilic fibres. Δ<i>H</i>ᵒ and Δ<i>Sᵒ </i>values were positive for all the dyeings. The apparent diffusion coefficient was highest for wool and lowest for silk.</span>