SYNTHESIS AND CHARACTERIZATION OF SOME AMPHIPHILIC STYRYL DYES AND THEIR APPLICATION ON WOOL FABRIC
CHAPTER ONE
1.0 INTRODUCTION
1.1 Dyes
A dye is a coloured compound that has affinityand able to be retained on the substrateto which it is applied. The dye is generally applied in an aqueous solution, and may require a mordant to improve the fastness of the dye on the fibre.Both dyes and pigments appear to be coloured because they selectively absorb some wavelength of visible light. In contrast with a dye, a pigment is generally insoluble in the media in which they are applied. Some dyes can be precipitated with an inert salt to produce a lake pigment, and based on the salt used they could be aluminum lake, calcium lake or barium lake pigments (Zollinger, 2003).
Dyed flax fibre has been found in the Republic of Georgia dated back in a prehistoric cave to 36,000 BC. Archaeological evidence shows that, particularly in India and Phoenicia, dyeing has been widely carried out for 5,000 years. The dyes were obtained from animal, vegetable or mineral origin, with none to very little processing. By far the greatest source of dyes has been from plant kingdom, notably roots, berries, bark, leaves and wood, but a few have ever been used on a commercial scale (Zollinger, 2003). Dyes can be broadly divided into two major types i.e. Natural and Synthetic dyes
1.1.1 Natural Dyes
The majority of natural dyes are from plant sources – roots, berries, bark, leaves wood, fungi and lichens. Throughout history, people have dyed their textiles using common, locally available materials. Scarce dyestuffs that produced brilliant and permanent colours such as the natural dye tyrian purple and crimson kermes were highly prized luxury items inthe ancient world. Plant-based dyes such as woad, indigo, saffron and madder were produced using resist dyeing techniques to control the absorption of colour in piece-dyed cloth. Dyes such as cochineal and logwood were introduced in Europe by the Spanish treasure fleets, and the dyestuffs of Europe were carried by colonists to America (Zollinger,2003).
The use of natural dyes in textile application is gaining popularity because of the quality of the natural colour obtained as well as the environmental compatibility of the dyes. In addition, natural dyes can exhibit antimicrobial and deodorant properties. Nevertheless their inferior fastness compared to synthetic dyes is a deterrent to their use as there is difficulty in extracting and storing the colourant (Deo and Dasa, 1999). The discovery of man-made synthetic dyes late in the 19th century ended the large-scale market for natural dyes.
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SYNTHESIS AND CHARACTERIZATION OF SOME AMPHIPHILIC STYRYL DYES AND THEIR APPLICATION ON WOOL FABRIC
