Meaning
Compounding raw plastic resins with highly concentrated additives or pigments requires a carrier medium to ensure uniform distribution during the final moulding process. This concentrated mixture is called a masterbatch and it is added to virgin polymer in a specific ratio during extrusion or injection moulding. The carrier resin must be compatible with the base polymer to avoid phase separation or mechanical weakness.
It does not replace the primary resin but serves to modify its color, stability, or physical properties.
Additive Dispersion
High concentrations of pigments are dispersed in a polymer matrix during a compounding step. This pre-dispersion ensures that fine powders do not agglomerate during the subsequent moulding stage.
Process Integration
Moulding shops feed the concentrated pellets into the machine hopper along with the primary resin using a gravimetric or volumetric dosing unit. During the melting phase, the carrier resin melts first and distributes the active ingredients evenly throughout the polymer melt. This method prevents the dust and contamination hazards associated with handling loose powder pigments on the production floor.
Economic Advantage
Purchasing natural resin in bulk and blending it with a concentrated masterbatch is cheaper than buying pre-colored polymer compounds from a resin distributor. This dosing method reduces inventory costs by allowing a single base resin to be used for multiple product colors or grades, which optimizes warehouse space. The dosing ratio must be controlled carefully because too much carrier resin can reduce the mechanical properties of the finished part, particularly in structural applications where impact resistance is required.
