Studies on the drawing of polyamide fibers. VI. Effect of drawing on the dye diffusion parallel to the fiber axis

The diffusion rate of an acidic dye (vylene Fast Blue 2P) into polycaproamide fibers along the direction parallel to the fiber axis (longitudinal diffusion rate) was obtained by measuring the dye penetration distance from a cross section of the sample fiber embedded in an acrylic resin. The following results were obtained. The longitudinal diffusion constant decreases monotonically with increasing draw ratio. The difference between the lateral dye diffusion constant and the longitudinal dye diffusion constant passes through a maximum near a draw ratio of 2. The activation energy for the longitudinal dye diffusion increases monotonically with draw ratio.