|MadSci Network: Chemistry|
When coloring fabric, the type of dye used depends on the type of fabric that is being dyed. In general, the proper dyes bond covalently to the specific fabric. For instance, negatively-charged dyes will bond to fabric containing positive charges. Pigments, on the other hand, can also be used to color fabrics. Pigments generally attach via absorption. Fiber-reactive dyes work differently in comparison to all other dyes: they are not bonded directly to fabric. Instead, they are anchored to the fabric. Specifically, dyes whose molecular structures contain hydroxy (- OH) or amine (-NH2) groups are reacted with cyanuric chloride (C3N3Cl3). Cyanuric chloride serves as the anchor. The dye covalently bonds to C3N3Cl3 by replacing one of the chlorines (Cl). The resulting product of the reaction is called a "Procion dye". When the Procion dye is put in contact with fabrics that also contain -OH and/or -NH2 groups in its structure, the remaining two chlorides on the cyanuric part of the Procion dye are replaced with the fabric via covalent bonds. Thus, fiber-reactive dyes are covalently bonded to the cyanuric chloride which is, in turn, covalently bonded to the fabric.
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