Biocolourants from onion crop side streams and forest mushroom for regenerated cellulose fibres

Biocolourants and sustainable textile materials have gained growing interest. Traditionally natural dyes have been used for dyeing wool and silk, but demand for cotton and regenerated cellulose fibres increases because of their popularity especially in clothing. This study expands the natural dye research to one of the latest innovations among regenerated cellulosic fibres, i.e. Ioncell®. It explains for the first time the dyeability of Ioncell–F fibres with biocolourants and compares the results with three other regenerated cellulose fibres, i.e. viscose, bamboo viscose and lyocell, using protein fibre wool as a reference. The colourants from the food side stream, the yellow onion (Allium cepa cv. Settonia) and the forest mushroom Cortinarius semisanguineus were used as dyes. The composition of colourants in each dye sources was analyzed in detail. Methods of exhaust dyeing (80 °C, 1 h), with alum, FeSO4 and tannin as mordants, and the high temperature high pressure dyeing (130 °C, 1 h) were applied. The colour of the dyed materials was studied as CIE L*, a*, b*, C*ab, hab and the K/S (λ420/480 nm) values. The colourfastness to washing and light was examined according to the ISO standards. The results showed that for regenerated cellulose fibres the strongest colour was obtained with polyphenols in acidic conditions, whereas with the anthraquinones the dyeing results remained light revealing hindering forces between the dye and the fibre. The colourfastness values were at highest for iron and aluminium mordanted samples, which indicate the metal ions’ ability to stabilize the organic compound’s structure and form strong coordination bonding between the fibre and the dye. The colourfastness varied from poor to moderate. The exhaustion levels between different regenerated cellulose fibres varied very little. The search for sustainable colourants, fibres and their applications in long lifetime artefacts is strongly supported by the sustainability goals, and colourant production in connection with forest and agricultural industries support this emerging field.Peer reviewe