I. Characteristics of Pearlescent Pigments: Pearlescent pigments are mica flakes coated with metal oxides to produce a pearlescent luster. They are acid-resistant, alkali-resistant, and heat-resistant up to 850°C. They are non-pyrophoric and exhibit excellent stability.

II. Formulation: The amount of pearlescent pigment added depends on the desired effect. The addition level is typically between 5-10% by weight of the solids content. For special effects or very thin glossy coatings, the dosage may be as high as 30%. However, higher levels are not recommended as they interfere with the orientation of the flake pigments, resulting in a loss of gloss. Sometimes, only 1%-1.5% of the solids weight is needed to achieve a more translucent clear coat.

III. 3. Wetting and Dispersion

IV. To facilitate dispersion of pearlescent pigments, pre-wet the pigment. Wetting time should be at least 20 minutes. First, it is recommended to mix the powdered pigment with a portion of the liquid system, or a compatible solvent, diluent, or plasticizer, to form a slurry. This slurry should then be evenly stirred into the remaining components. Pearlescent pigments can be dispersed using a standard agitator, similar to metal powders. The correct mixing method is to add the pearlescent pigment to a carrier that is being stirred using low-shear, axial flow technology. The pigment should not be added all at once; it should be added gradually. Once the first portion is fully wetted, continue adding until the entire portion is wetted. Continue stirring for 15 minutes to further disperse the pigment. An axially rotating agitator can be used for mixing. The pigment dosage should be less than 10%, and the stirring speed should be moderate. During the stirring process, the stirring paddle height should be varied to prevent uneven mixing in the dead zone directly below the agitator. The particle size and associated brittleness of pearlescent pigments only allow for very low shear forces during dispersion. Do not use machines used to mix conventional pigments, such as roller mills, ball mills, or stone mills, as these can damage the crystallization of pearlescent pigments and cause loss of gloss. If a disperser is used, a shorter mixing time is recommended. It is recommended that the same mixing time and speed be used for each batch of paint under the same conditions.

V. IV. Stability:

VI. Pearlescent pigments generally do not flocculate. There are two ways to minimize pigment settling in paint systems: 1. Preventing pearlescent pigment settling through good wetting and dispersion, as described above; 2. Ensuring that the pigment is well suspended in the vehicle. Special additives, such as thixotropic agents, can be added to the vehicle to improve the settling behavior of pearlescent pigments in paints. Organically modified bentonites, polyethylene waxes, and other organic thixotropic agents that are less detrimental to pearlescent pigments can be used. Pyrogenic silica is not recommended because it is a matting agent and can significantly reduce gloss and color performance even in small amounts. Sometimes, the settling of relatively large and heavy pigment platelets necessitates the use of a flocculant to create a controllable flocculation. This results in a loose, easily dispersible precipitate that is unstable under external forces and can be easily stirred to restore the original uniform paint mixture.

VII. V. Particle Size Selection:

VIII. Pearlescent pigments are available in a variety of particle size distributions. Particle size affects the gloss, hiding power, and appearance of a paint. As the flake size increases, the sparkle increases. The ideal particle size distribution is 10-40 μm. Larger particles create a shimmering effect with less hiding power, while smaller particles create a softer, satin finish with greater hiding power.

6. Color Mixing:

Pearlescent pigments can be combined with conventional pigments to create a wide variety of vibrant, high-purity colors, such as phthalocyanine blue and phthalocyanine green. However, it's important to avoid using too much colorant, as excess light-absorbing color can obscure the pearlescent effect at reflective angles.

7. Hiding Power:

There are several ways to improve hiding power in a formulation:

A: Fine-particle pearlescent powder can improve hiding power. However, the pearlescent effect is a softer satin finish, and the shimmer is less pronounced. To achieve the desired pearlescent effect and hiding power, replace some of the coarser pearlescent powder with finer particles.

B: Adding metallic powders to the paint, such as aluminum powder and copper powder, can improve hiding power. The typical dosage is 5-10% of the pearlescent pigment.

C: When mixing dark colors, a small amount of carbon black can provide excellent hiding power, and adding black can enhance the reflective color of the pearlescent. D: When blending lighter colors, titanium dioxide can also significantly improve hiding power. However, this can reduce the pearlescent effect. Therefore, if titanium dioxide is used, the amount of pearlescent pigment should be increased to enhance the reflected color. A small amount of titanium dioxide should be used, just enough to achieve the desired hiding power. Remember: opaque pigments or dyes will reduce the pearlescent effect.

In summary: Pearlescent pigments are versatile, offering a range of soft satin sheens, shimmering effects, and metallic lusters.

Formulations based on the following three principles can achieve optimal pearlescent effects:

1. Use an appropriate amount of pearlescent pigment to create numerous reflective/transmissive surfaces, resulting in a good pearlescent effect;

2. Ensure the pigments are aligned in parallel to achieve a better specular reflection;

3. Ensure the paint surface is transparent to allow light to pass through unimpeded.