Masterbatch Questions & Answers

A plastic masterbatch is made from a concentrated mixture of pigments and/or additives compounded into a carrier resin. Masterbatches are mixed into a base material at a specified addition rate in order to give the desired colour or property once the material has been made into the finished article.

The amount of masterbatch which is required to be added to the base material to give the correct colour/effect is known as the addition rate and is usually expressed as a percentage.

Typical addition rates for masterbatches are between 1% and 5%, depending on the pigments being used and the base polymer, but can be as high as 30-40% in some instances.

Masterbatches are manufactured using a carrier polymer and the required additive eg colourants, flame retardants, UV stabilisers etc.

The polymer carrier needs to be at a percentage level which enables easy mixing of the additive into the base material. If a large amount of additive is required to give the required effect this may lead to there not being enough carrier polymer to enable the masterbatch to blend consistently with the base polymer. In this case the carrier polymer level needs to be increased and therefore the addition rate needs to go up accordingly to ensure the correct amount of the required additive is in the mix.

When looking at the cost of a masterbatch several things need to be taken into consideration. This includes the stability of the pigments being used and what the addition rate of the masterbatch is.

The cost of the pigments in coloured masterbatch are very much dependant on the quality and the stability of the pigments being used. Higher quality more stable pigments tend to be more expensive than less stable ones. This stability can affect the colour properties during moulding process and in the final product.

Avient masterbatches are generally formulated using the highest quality pigments which allow a low addition rates, typically 1%, and excellent colour stability. This can make them seem more expensive than alternatives on the market, but can reduce the possibility of issues further on and therefore be cost effective.

Masterbatches can be added to polymers in several ways. The easiest method is to add the correct level of masterbatch to the base polymer and mix by hand in either a polythene bag or mixer until the masterbatch looks reasonably well dispersed.

Another commonly used method is to use a dosing machine or screw which, during the processing of the plastic material, introduces a controlled amount of masterbatch into the base material. This method gives a more even and controlled addition than mixing by hand.

A universal masterbatch is a masterbatch which can be used in a variety of polymers. This is because the base polymer is compatible with a range of base materials. It should be noted that not all universal masterbatches are compatible with all base materials.

A polymer specific masterbatch is a masterbatch which has been formulated using the same base polymer as it is going to be used in. These tend to be used where a universal masterbatch does not give a good result in the polymer concerned.

The short answer is no. To ensure even dispersion of a masterbatch it needs to be thoroughly mixed into the polymer. This requires the mixing screw of a conventional moulding machine. If run using a plunger machine this mixing will not take place and result in streaks of colour in the moulded part rather than an even colour.

Omnicolor™ colour masterbatches do not need drying. If using in a material which does, they can be added before drying providing the drying temperature does not exceed 100 deg C. For materials which need a higher drying temperature masterbatch should be added after drying.