Mica pearl pigments are quite common in our daily lives, but we may not be very familiar with them. Here are some factors that affect the quality of mica pearl pigments for your reference.

(1) Particle morphology and aspect ratio of the matrix mica powder: The matrix mica powder is the carrier for depositing and coating nano-titanium dioxide particles. The particle morphology and aspect ratio of the matrix mica powder have a significant impact on the quality of mica pearl pigments. Generally, the aspect ratio of the matrix mica powder used to prepare mica pearl pigments is required to be greater than 50.

(2) Inclusions in mica flakes: The chemical composition of natural sericite raw materials is complex, especially the coloring metal ion oxides such as iron, manganese, chromium, and vanadium. These not only directly affect the original whiteness and gloss of the mica flakes, but also affect the whiteness and gloss of the pearl pigment after chemical deposition reaction coating. This effect is particularly pronounced when manufacturing pearlescent pigments with high whiteness and gloss, resulting in low whiteness, poor gloss, and grayish, yellowish, or blackish colors. If mica flakes with high impurity content are used to manufacture iridescent and colored pearlescent pigments, the pigment exhibits color shift and a decrease in chroma.

(3) Process factors in the coating process: For chemical liquid phase deposition processes, the process factors in the deposition and coating process are closely related to the hydrolysis reaction of titanium salts, the deposition of hydrolysis products on the mica matrix to form a nanoparticle coating film, and the growth of the film. In particular, pH value, temperature, stirring speed, and reagent dripping rate have a significant impact. In experiments, the parameters of these factors are determined to adjust and control the processes of the aforementioned steps. Studies indicate that regardless of the type of mica pearlescent pigment being manufactured, the reaction must be carried out under relatively constant reaction conditions such as pH and temperature. This ensures that the hydrolysis rate of titanium salts and the nucleation and growth rates of hydrated titanium dioxide particles are stable and harmonious, resulting in a uniform, smooth, and dense titanium dioxide particle coating layer. Rough, uneven pigment particle surfaces diffusely reflect light in various directions, causing interference between reflected light and reducing gloss. Only smooth surfaces can achieve unidirectional light reflection, and parallel reflected light enhances gloss.

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