Steam and heat setting of nylon 6 fiber. X. Effect of heat setting on diffusion of dyestuff into nylon 6 fiber

The degree of penetration, the diffusion constant, and the uptake of dyestuffs of different molecular sizes were measured in undrawn and drawn nylon 6 filament, heat-set under various conditions in order to determine the pore structure in the amorphous regions. Unset and dry-heat-set nylon 6 can be penetrated only with difficulty by the dyestuffs having molecular lengths above about 30 and 25 A., respectively. The apparent diffusion coefficients and molecular weight of dyestuffs are approximately hyperbolic. The relations are considerably different, depending on the degree of drawing and conditions of the heat setting. Further, the relations among molecular size, amount of absorbed dyestuffs, and fraction of amorphous region capable of being penetrated by dyestuff are discussed with reference to the lateral-order distribution of nylon 6, as evaluated from the accessibility to D2O vapor.