Tips | How to improve the blackness of polyester fabric when dyed black?

When pure polyester fabrics are dyed with disperse dyes, especially filament fabrics, they always look bright and white after dyeing. Increasing the dye concentration will not help, and the dye fastness will be greatly reduced.
There are two reasons for the low blackness:


The cross-section of polyester fiber is smooth and circular, and the reflection of light is more specular, that is, the white light is more concentrated, so it does not look black.


The refractive index constant of polyester fiber is the largest among all fibers. For example, the refractive index of wool is 1.553, silk is 1.598, viscose fiber is 1.577, nylon is 1.580, and polyester is 1.725. An object with a large refractive index has a large reflectivity. The reflected light is reflected in white light, so it looks white.

In addition, the high reflectivity means that the amount of light absorbed is reduced, so the color depth is not large.


For this reason, some people have tried to apply a material with low refractive index to the surface of the fabric, so that the refractive index of the fabric is reduced, the reflectivity is also reduced, and the blackness is improved. This low refractive index resin polymer is mainly acrylic compound, which can form a polymer film on the surface of the fabric.

After treatment with this resin polymer, the fabric depth index is significantly increased, and the visual depth can be increased by more than 20%.


The dyed fabric can be dried by dipping or padding the polymer. The bath ratio is 1:30, the temperature is 80℃, and the time is 30min. After applying the polymer, not only the blackness is improved, but also the vividness of the shade is improved, the gloss is soft, and the durability is good, and the shade is unchanged.