Nylon 6 filament (φ5=900μm) was dyed with aqueous dispersion of two different dispere dyes, one of which is azobenzene based and the other is anthraquinone based, at 40°C, 60°C and 80°C and the concentration gradient of the dye molecules penetrated along and perpendicular to the fiber axis were determined by an optical microscopy and a microspectrophotometry.
The rates of penetration of both dyes penetrated starting at the sliced cross section then diffusing along the fiber axis (=D_??_) at three different temperatures were compared with those penetrated laterally through the surface of the filament (=D_??_), respectively on each profiles of relative dye concentration (=Absorbance)-penetrated distance.
It was found that D_??_ is about three times faster than D_??_ for the nylon filament examined in this study. Taking into account of the glass transition temperature of solid nylon 6 is of the order of 70°C, it was confirmed that, at 40°C, both dyes are effective to give colored texture only at the periphery of the filament. At 60°C, it is seen distinct differences between the profiles of dye concentration-penetrated distance for both dyes. The dye bath temperature about 80°C is adequate to give distinct differences between those profiles as Disperse Blue 3 tends to an equilibrium showing homogeneous coloration throughout the texture while Disperse Red 1 attains another type of equilibrium having rather wide spreaded concentration gradient with an absorption maximum.
It was also confirmed on these profiles that the highest dye concentration (=absorption maximum) is not found at zero distance. i.e., at the periphery of the sample filament but appears at the interior part of about 100_??_200μm from the surface.
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