Effect of Radiation on Textile Dyeing

Love for colours is a natural instinct and every individual has his own choice and liking for colour. The icy appearance of Hamaliyan ranges or lush green forests or fields of agriculture or trees laden with colorful fruits or butterflies moving from flower to flower presents the beauty of nature, generation after generations are being attracted. The choice of beautiful fascinating colours reflects the aesthetic sense of humans that varies. Colour is visual perceptual property corresponding in humans to the categories called red, yellow, blue and others. It is a sensation that arises from the activity of retina of the eye and its attached nervous mechanism, and results in a specific response to the radiate energy of certain wavelength and intensity. Thus it is a quality of an object with respect to light (Mizzarini et al., 2002).Colorants may be either pigment or a dye which are characterized by their ability to absorb or emit light in the visible range 400-700nm.They may be organic or inorganic depending upon their structure and method of production. Dyes are the coloured substances which are capable of imparting their colours to the matrix which may be fiber, paper or any object. They must have fixing tendency on a fabric that is impregnated with their solution and the coloured fixed dyes must be fast to light as well as resistant to action of water, dilute acids, alkalies, various organic solvents used in dry cleaning, soap solutions, detergent, etc ( Shukla, 1992 ) . A pigment generally is a substance which is insoluble in the medium in contrast to dye in which it is applied and has to be attached to a substrate by additional compounds e.g. polymer in paints and plastics (Taylor and Nonfiction, 2006) A compound looks coloured because it has absorbed certain electromagnetic radiation from the visible region. The moieties, present in colouring substance, responsible for the absorption of electromagnetic radiation and reflect in the visible region are called chromophores (Younas, 2006).Ultraviolet radiation constitutes to 5% of the total incident sunlight on earth surface (visible light 50% and IR radiation 45%). Even though, its proportion is quite less, it has the highest quantum energy compared to other radiations. Light is electromagnetic in nature. Within the electromagnetic spectrum, human eye captures visible light in the range between about 380 nm and 700 nm (Mizzarini et al., 2002). Dyes absorb electromagnetic radiation of varying wavelength in the visible range of