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ABSTRACT. An attempt was made to extract natural colourant from the bark of N. papaeverifera. The optimisation of the extraction procedure was evaluated using various solvents. The optimal colourant extraction was observed with acetone as solvent at constant temperature of 70 °C for 1 h. The main extracted colourant compound was isolated using column chromatography and characterised by ultraviolet-visible spectrophotometer, mass spectrometry, proton and 13C nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. The dyeing and durability of the colourant extract were evaluated. This low-cost biomass was obtained from a timber industry and its extract used to dye cotton and nylon 6,6 fabrics with only small amounts (6% and 4%) of metallic mordants, namely, copper(II) sulfate and stannous chloride. Dyed cotton and nylon were analysed for their K/S, CIE L*, a*, b*, c*, h* values and the colour fastness properties to light, crocking (rubbing) and washing. The UV-visible spectral result suggest the presence of such chromophores as C=O and –C=C–. The broad FTIR result at 3596 cm-1 is indicating a carbonyl group, the 13C NMR spectrum showed absorption at 206 ppm while the proton NMR gave absorption at 4.37 to 5.24 ppm suggesting –OH protons. Colour shades of brown were obtained. Significant differences in colour depth were observed depending on the mordant type. Copper(II) sulfate was found to produce the most significant colour changes, the deepest brownish colour, and the best light fastness and wash fastness values. The colourant extract itself (without mordant) had a light fastness of 3 (fair) on cotton fabric and 3/4(good) on nylon 6,6 fabric. In general, colour fastness to light was good (grade 5 for cotton and grade 4/5 to 5 for nylon) colour fastness to washing was very good (grade 4 to 4/5 for cotton and grade 3/4 to 4 for nylon) and colour fastness to rubbing was very good (grade 3/4 to 5).
KEY WORDS: Natural colourant, Optimised extraction, Mordanting, Percentage of dye absorbed, Fastness
Bull. Chem. Soc. Ethiop. 2019, 33(3), 415-424.