How to make polyester fabric deep and bright?

The reason why the dyeability of polyester fabric is worse than that of natural fiber is that the polyester fiber is thinner and the specific surface area is larger, so that the reflected light (achromatic light) on the surface of the fiber is increased, and the colored light reflected (or transmitted) by the light coming into the fiber is less, so the color becomes lighter in the visual effect. That is to say, the surface color depth is obviously reduced. Therefore, it is necessary to add more dyes to polyester fabric to achieve the required surface color depth. In actual production, sometimes even if the amount of dye is increased, the surface color depth required by customers can not be reached, and the color fastness of dyed polyester fabric will be affected. In order to increase the visual surface color depth of polyester dyed fabric without adding dyes, the darkening agent can be used to darken and brighten the polyester dyed fabric.