Dye diffusion in anisotropic polyamide fibres

Radioactive tracer techniques have been used to study the diffusion of three dyes in polyamide fibres produced under different conditions. It has been shown that drawn nylon fibres have a surface barrier layer which limits diffusion. The permeability of the layer is reduced by drawing, and varies with drawing conditions. The dependence of dye diffusion on concentration, ionic size and draw ratio is less in the surface than in the bulk of the fibre, but variations in dyeing behaviour have been shown to follow surface rather than bulk diffusion characteristics.