The influence of reactive dyes on the pyrolysis of cotton

The influence of reactive dye, Procion Red HE 3B, on the pyrolysis of cotton was studied, using TGA, DSC and Py-GC–MS methods. The dye, when applied at a high concentration, lowered the decomposition temperature of cotton from 375 °C to 325 °C, and increased the production of residual solids. This effect was attributed to the covalent bonding of the dye molecules to the hydroxyl groups of cellulose, creating a cellulose copolymer and blocking the path for the formation of levoglucosan and volatile products. The pyrolysates of cotton and dyed cotton were different at lower temperatures (300–500 °C), indicating that different mechanisms of pyrolysis were operative at those temperatures. At higher temperatures (700–900 °C), the pyrolysates of cotton and dyed cotton were similar, indicating that the dye had no influence on the mechanism of pyrolysis at such high temperatures.