Masterbatch is a solid or liquid additive used to impart color to plastic products or improve their performance. It mainly comes in two types.
Masterbatch can be divided into two categories: one is pigment-concentrated masterbatch, and the other is performance-enhancing masterbatch used to improve the properties of final plastic products. During plastic production, masterbatch is added to the base polymer to ensure cost-effective coloring of the polymer.
The colorants used in masterbatch must be compatible with plastic resins and additives.
The colorant should not react with resins or other additives and must have strong solvent resistance, low migration, and good heat resistance. In other words, the colorant should not participate in any chemical reactions. For example, carbon black can interfere with the curing reaction of polyester plastics, so it should not be used in polyester applications.
Since plastic processing temperatures are generally high, colorants must not decompose or change color under molding conditions. In general, inorganic pigments have better heat resistance, while organic pigments and dyes are relatively weaker in this aspect, which should be carefully considered during selection.
Colorants must have good dispersion and strong tinting strength. Poor dispersion will affect product appearance, while weak tinting strength will require higher usage levels, increasing material costs. The same colorant may show different dispersion and tinting performance in different resins, so this must be taken into account during selection.
Pigment particle size is also related to dispersion performance. The smaller the particle size, the better the dispersion and the stronger the tinting strength.
It is also important to understand other characteristics of pigments. For example, pigments used in food-contact and children’s toy products must be non-toxic; pigments used in electrical products should have good electrical properties; and pigments used in outdoor applications should have excellent weather resistance.
Masterbatch is mainly used for plastic coloring, and there are many types of plastics such as PP, PE, PC, ABS, PVC, PA, and PBT. When adding masterbatch to different plastics, compatibility must be considered; otherwise, poor dispersion may occur and the mechanical properties of the base material may be reduced.
Different processing technologies require different dosages of functional masterbatch. Injection molded products generally require lower addition levels due to their thicker structure and deeper color coverage. Film products are much thinner and therefore require higher masterbatch concentration and dosage; otherwise, the color will appear too light.
Various masterbatches may absorb moisture after storage, especially PET, ABS, PA, and PC types. Therefore, they should be dried using the same process conditions as raw resin pellets to meet moisture content requirements.