The dye attaches to the fibre through a chemical reaction triggered by alkaline conditions (high pH). There are two main types of reaction mechanisms: 1. Nucleophilic Substitution
Excellent, because the dye is chemically locked to the fibre. The Chemistry of Synthetic Dyes. Reactive Dyes
Common in dyes. The chlorine atom on the dye molecule is displaced by the hydroxyl ( OHcap O cap H ) group of the cellulose or the amino ( NH2cap N cap H sub 2 ) group of protein fibres. Result: A stable carbon-oxygen or carbon-nitrogen bond. 2. Nucleophilic Addition The dye attaches to the fibre through a