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Reactive dye is the dye that can react with a fibre to form a covalent link, that is forming a permanent attachment in the fibre and could not be removed by repeated treatment with boiling water under neutral conditions. Consequently, the dyes become parts of the fibre, leading to outstanding colour fastness to wash.
Due to the advantages of full colour ranges, brightness, high fastness, low cost, easy application, etc., reactive dye became the predominant dye for cotton dyeing and printing in textile industry since it was invented. Compared with direct dye, reactive dye is applied as easy as direct dye but has very high levels of fastness, especially for wet fastness.
