What are the effects and precautions of pearlescent pigments

If the object reflects all the white light illuminated, it appears white; if it is partially reflected and partially absorbed, it is gray; when it is almost completely absorbed, it appears black. If an object appears red, it is because of the incident white light, only the red wavelengths are reflected, and the rest of the color light is absorbed. Generally, pigments are added to the color developing agents of plastics, coatings and inks, and the light is absorbed, diffused, and penetrated by the pigments to display different effects such as color, gloss or transparency of the object.

The pearlescent effect produced by the interference of light can be understood from the example of oil floating on water. This iridescent color occurs due to the interference and enhancement of specific wavelengths of visible light reflected from the air/oil interface at the top of the film and the oil/water interface at the bottom at the same time.

The pearl luster of pearlescent pigments comes from a titanium dioxide layer deposited on mica flakes with a strictly controlled film thickness. When light hits the flakes of pearlescent pigment there are many paths. Some light passes through the air or the interface with low refractive index near the pearlescent pigment (such as the resin of the coating film), and when the light hits the surface of the titanium dioxide layer, it is reflected, which is caused by the high refractive index of titanium dioxide and the difference in the refractive index of the resin and titanium dioxide interface . Part of the light passes through the titanium dioxide layer and is re-reflected at the interface between the titanium dioxide layer and the mica. In this way, through multiple reflections and refractions, the pearl luster can be produced.

The resulting color depends on whether the light reflected from the two different interfaces reinforces or interferes with each other. The change of titanium dioxide film thickness will cause the change of color light. The optical thickness of the transparent film (the multiplication of the geometric thickness and the refractive index) is a prerequisite for the occurrence of light interference. Since the interfering color changes with the light and the angle of viewing, iridescence appears.

Compared with metallic pigments, pearlescent pigments have the following advantages:
● It is non-conductive and is an insulator. During high-voltage and high-frequency processing, it will not cause the danger of sparks due to electrification.
● Good acid and alkali resistance, no discoloration.
● Insoluble in water, but can be dispersed in water, suitable for the processing of water-based products.
● High temperature resistance up to 800℃, no spontaneous combustion, no combustion support.
When pearlescent pigments are mixed with transparent substances such as plastics, coatings and printing inks, the pigment particles are arranged in parallel with the surface, and a beautiful pearl luster can be produced due to the multiple reflection and refraction of light. Pearlescent pigments are mixed with carbon black or transparent colorants to obtain metallic luster similar to gold, silver, copper, aluminum, etc. And if the pearlescent pigments of the color red series are mixed with carbon black or transparent pigments, they will produce a very unique metallic luster.

Matters needing attention when using pearlescent pigments
1. Pearlescent pigments can be used together with transparent dyes or pigments to obtain unique and beautiful color effects, but if used together with opaque pigments, the pearl luster will be reduced.
2. High shear mixing or long-term mixing will destroy the particles of pearlescent pigments, which is the reason for the reduction of pearl luster.
3. When the ink or paint has a low viscosity, the pearlescent pigment particles will precipitate. Please stir again when using.
4. Due to the phenomenon of complementary colors, please do not mix the rainbow-colored series of pearlescent pigments.