How to use pearlescent pigment in Plastics

Can mica pearlescent pigments be uniformly dispersed and directionally arranged in plastic resins, affecting the pearlized color effect? This is a crucial aspect.

(1) Rotational Molding

In rotational and centrifugal molding processes, start by preparing a concentrated slurry of plastic resin and pearlescent pigments. Pour this concentrated pearl slurry into a rotating drum with a smooth inner surface. Under the influence of centrifugal force, the resin adheres uniformly to the drum’s surface, causing pearl pigments to align parallel to the drum’s surface. For polyester resin injection molding, the recommended pearlescent pigment addition is generally 1.5% to 5% of the resin mass. Adjust the quantity based on resin transparency and color intensity.

Formulation Example:

Purpose: Pearlized polyester button blanks

Quality Requirements: Should exhibit a pearl luster and possess sufficient hardness, flexibility, and withstand drilling and cutting processes.

5~25μm sapphire blue or emerald green iridescent pearl pigment: 11.5g

Polyester resin + styrene monomer (950g of polyester resin): 1000g

Diacetyl peroxide: 10g

Zinc cobaltate: 0.75g

UV stabilizer: 3g

Ensure resin viscosity is around 104mPa·s; adjust with styrene monomer if viscosity is too high. Solidification time at room temperature should be controlled around 8~10 minutes.

(2) Flat Injection Molding

Pour the well-mixed resin mixture into a mold made of flat glass or stainless steel and immerse it in a water bath at 70~80℃. To achieve directional arrangement of pearlescent pigments, fix the mold on a guide rail capable of reciprocating motion. When the mold moves horizontally back and forth, pearlescent pigments close to the mold’s bottom move with the mold wall due to friction, resulting in a uniform and fine directional arrangement during the curing process.

Formulation Example:

5-60um silver or iridescent pearlescent pigment: 12.5g

Acrylic monomer: 8.5g

(Pre-mix the above two components into a concentrated pearl slurry, then mix uniformly with the following components)

Polyacrylic resin solution: 1000g

Mercapto peroxide: 10g

UV stabilizer: 2.5g

(3) Extrusion Molding

Extrusion molding is mainly used for producing continuous profiles and plastic pellets, such as plastic pipes, rods, cable coatings, and plastic profiles.

Formulation Example:

Purpose: Pearlized cosmetic packaging bottles, safety helmets, pearlized plastic basins, buckets, trays, and bathroom components.

PET, AK, LDPE, PP, PS, etc.: 1000g

560μm silver or iridescent pearlescent pigment: 8.5~10g

Acrylic monomer or styrene monomer: 5.0g

Plasticizer (dibutyl phthalate): 3.0g

UV stabilizer (such as 2,4-di-tert-butylphenol): 2.5g

Heat stabilizer (such as antimony thiol): 2.5g

(4) Biaxial Stretching

Biaxial stretching is ideal for producing plastic films (BOPP) with the best pearlized effects. It enhances the directional arrangement of pearlescent pigments in the resin.

Formulation Example:

Purpose: Pearlized films for ice cream, soft drinks, biscuits, candies, and napkin packaging.

PET, LDPE, PP, PS, etc.: 1000g

45% content of 5~25μm silver pearlescent pigment masterbatch: 6.75g

Corresponding monomers: 5.0g

Plasticizer (triphenyl phosphate): 2.5g

Photothermal stabilizer (QU-10): 2.5g

Please note that technical terms and measurements have been retained to maintain the accuracy of the information. If there are specific terms or phrases you’d like further clarification on, feel free to ask!


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