Common Dyes and Their Properties
This ready reference addresses the classification, properties, bonding, mode of manufacturing, and application areas of dye materials.
TABLE OF CONTENTS Common Dyes and Their Properties
Bonding of a Dye to Fiber
The process of dyeing depends not only on the type of the dye but also on the type of fiber. Fibers can be natural or synthetic. Natural fibers are cotton, linen, flax, hemp jute, wool, silk, and leather and fur. Polyamides, polyesters, and polyacrylonitrile are some examples of synthetic fibers.
There are four ways by which a dye molecule can be bonded to the fiber:
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Covalent bond
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Hydrogen bond
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Ionic bond
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Van der Waals forces
Covalent Bond
Covalent or chemical bonding occurs in a chemical reaction between the fiber and the dye. This reaction occurs when the fiber is clean and the dye is in close contact with the surface. The chemical bond is the most heat resistant of all types of bonds. Dyes that form such bonds are long lasting and do not fade easily on exposure to sunlight and chemicals.
Hydrogen Bond
Hydrogen bonding occurs when there is a strong electrical attraction between the dye and the fiber. Hydrogen bonding is possible with polar fibers.
Ionic Bond
An ionic bond occurs when oppositely charged ions are attracted. Acid dyes contain a sulfonic or a carboxylic group, which forms a strong salt linkage to a basic group in the wool molecule. The strength of this bond is responsible for the wash fastness of good acid dyes.
Van der Waals Forces
Van der Waals forces are forces between molecules with closed shells. Consisting of several types of interaction, these forces are called Van der...
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