Masterbatch is a concentrated mixture of pigments and/or additives encapsulated during a heat process into a carrier resin which is then cooled and cut into a granular shape. Masterbatch allows the processor to colour raw polymer economically during the plastics manufacturing process.

The polymers
There are two polymer resins to be considered:

Carrier Resin
The resin in which the pigments and/or additives are carried and which forms the masterbatch.

Dilution Resin
This is the polymer or polymers which make up the bulk of the plastic processor's finished product.

The Colourants
There are three main types of colourant:

Inorganic Pigments
This type of pigment is manufactured from natural raw materials and includes fundamental types such as titanium dioxide, iron oxides and ultramarine blue. However many are not suitable for some applications such as packaging due to their toxicity. Pigments in this category include lead chromium and cadmium.

Organic Pigments
Organic pigment systems are synthesised and tend to have lower heat stability than inorganics. One of the big advantages of this type of pigment system is that they are normally non-toxic and conform to legislation relating to food contact and safety.

Dyestuffs
These are man-made soluble dyes, which are used extensively in fibre colouring, for example.
Their general use is limited due to their incompatibility with polyolefins, but they can be very effective in styrenics and engineering polymers. Dyestuffs have good colouring strength, but can be expensive.

The additives
Different types include:

Performance Additives:
To enhance the performance of the end product.

Processing Additives:
To aid the efficiency of manufacture.