A Review of Some Sustainable Methods in Wool Dyeing

Abstract

During the recent years, a good deal of research was carried out in developing natural dyes and mordants in dyeing of different natural fibres, which has paved the way towards achieving sustainability in the area of wet processing. This chapter highlights some significant trends in eco-friendly methods of wool dyeing. The influences of dye kind of mordant and dye concentration on the colour characteristics of dyed wool fibres have been studied. In order to quantify assessment of the influences of kind of mordant and concentration of dye, the calorimetric properties including colour strength, colour difference and colour coordinates have been considered. The findings reveal that the wool has great attraction for pinecone dye liquid, and mordant methods adopted show various shades between beige to brown which have good fastness. The reaction between diphenolic catechol and enzymes of potato juice has been used for optimization of wool colouration. No surplus chemicals are required for colour formation at low temperature. Investigation has been carried out on the effect of process variables such as temperature and corresponding concentration of catechol and plant juice on the colour intensity of the fabric. The temperature is found to significantly affect the colour strength. Wool dyed with different colours possess wash and light fastness. Fermented kum leaves have been applied on wool and comparative studies using traditional method of cold and heating process and chemical method using metallic salts have been investigated with regard to colour fastness properties, tensile strength and elongation percentage. The colour fastness in chemical as well as traditional methods exhibits fair to excellent results. The traditional hot method gives better results compared to the cold one. In order to study the colour fastness properties of colourant on wool fibres dyed with a natural dye extracted from the leaves of Symplocus Racemosa different mordants in combination with lemon juice have been used in suitable proportions. The test results of the dyed fabrics with regard to wash, rub, light and perspiration fastness have yielded fair to excellent fastness grades. Investigations have been carried out on kinetic and thermodynamic aspects of wool fabric using crude dye extract of A. Nobilis and compared with other natural dyes. Various dyeing parameters have been evaluated. All the dyeing methods discussed herein are good attempts to achieve sustainability. Each dyeing method offers its own merits besides achieving good properties. The advantages include optimization of dyeing process, better dyeability, affinity, flexibility in dyeing with other fibres besides wool, cost economy, improvement in properties, better utilization of natural resources, avoidance of harmful chemicals, etc.