Investigating the Structure of Nylon Fibers by Measuring the Diffusion Coefficient of Acid Dyes

The diffusion coefficient of CI acid blue 40 at 25°C was measured in samples of a nylon BCF carpet yam that had been heatset at 100% RH at temperatures ranging from 30 to 170°C. The diffusion coefficient at first dropped modestly as the heatsetting temperature increased, went through a shallow minimum, and then rose exponentially several orders of magnitude as the melting point of the yam was approached. Some speculations about the structural changes responsible for this behavior are offered.