Salt-free dyeing isotherms of cotton fabric grafted with PPI dendrimers

In this work, cotton fabrics grafted with poly (propylene imine) PPI dendrimers (second and fifth generations) were dyed with three different direct dyes (Direct Orange 34, Direct Red 83 and Direct Blue 199) using the salt-free dyeing method. Results showed that the color strength (K/S) of the grafted samples had been markedly enhanced compared with control samples. In addition, the equilibrium and kinetic data of the dye sorption process were evaluated using well-known mathematical models. It was found that the isotherm data of both direct dyes (Direct Orange 34 and Direct Red 83) followed the Langmuir sorption model, while the Freundlich model was able to describe the sorption isotherm of Direct Blue 199 on the grafted cotton fabric. Furthermore, the experimental data of the three direct dyes were fitted by the nonlinear pseudo-second order kinetic model. Wash, light and rubbing fastnesses of the dyed cotton samples were also investigated.