| Abstract: | The desorption of the hydrolysed forms of nine reactive dyes from wool has been examined in soap solution (ISO 2 test) and in urea-surfactant solution. It was found that the desorption of the hydrolysed dyes was slower in soap solution than in the urea-surfactant solution. After the standard 45 min of the ISO 2 washing test equilibrium was not reached, while after 60 min in the urea-surfactant solution equilibrium desorption was reached with most of the hydrolysed dyes. These findings clearly explain the discrepencies which sometimes occur between the two methods when used to assess wash fastness in relation to fixation ratios. If the time of the ISO 2 test is extended until equilibrium desorption is achieved then the two methods give essentially the same results. It was also found that the desorption rate constants appear to be inversely related to the molecular weights of the hydrolysed dyes. |
