Why is the blackness of polyester fabric dyed black not ideal?

When pure polyester fabrics are dyed with disperse dyes, especially filament fabrics, they always look shiny and white after dyeing. Increasing the dye concentration will not help, and the color fastness will also be greatly reduced.

There are two reasons for the low blackness:

1. 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.

2. 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 is 1.577, nylon is 1.580, and polyester is 1.725. Objects with a large refractive index have a large reflectance. The reflected light is reflected in white light, so it looks white.

Solution

To this end, someone has tried to apply a substance with a 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 depth index of the fabric is significantly improved, and the visual depth can be increased by more than 20%.

Approach

The dyed fabric can be dipped or padded with high polymer and dried. The liquor ratio was 1:30, the temperature was 80 °C, and the time was 30 min. After the application of the polymer, not only the blackness is improved, but also the brightness of the color is improved, the gloss is soft, and the durability is good, and the color is unchanged.