Sorption of Monobasic Dye-acid by Nylon-6 Fibre

Abstract

The equilibrium uptake of two typical monobasic dye-acids by nylon-6 (polycapramide) fibre has been measured for varying concentrations and additional evidence was given to confirm the mechanism of dye attachment to nylon as consisting of (1) combination with basic amine ends at normal dye bath pH and (2) combination mainly with the weakly basic nonterminal amide groups of the polymer chain at lower pH values. The Langmuir equation can well be applied to both regions of adsorption. It is well known that the thermodynamic affinity of a dye for the fibre represents a fundamental characteristics of the dyeing process. The anion affinities of dye-acids for nylon-6, calculated from data on the equilibrium distribution of dye-acid between bath and fibre in terms of the change in standard chemical potential of the dye sorption process using the equation for wool developed by Gilbert and Rideal, were in good agreement with values for nylon-66 obtained by other workers. Thus, the fundamental energetics of dyeing process and the mode of dye attachment are the same on these two fibres and some slight differences in dyeing behaviour must arise solely from differences in their physical structure due to the production process.