Concentrates, Masterbatches and Additives: What’s the Difference?

In the plastics industry, terms such as masterbatch and concentrate are often used interchangeably. The same applies to dosage, let-down rate, and dilution ratio.

Most of the time, this does not cause a major problem. But when we talk about formulations, costs, production planning, test results or product quality, it may be crucial to know exactly what is meant. These terms describe different concepts, even though industry usage is not always consistent.  

This article looks at the most common terms, what they mean in practice, and where misunderstandings can occur. 

Why not add the additive directly?

Direct addition can work in some cases, but in general powders and additives are difficult to feed and disperse consistently with machines that are intended for high production volumes.  There can also be challenges with dust and worker exposure.

For this reason, compounding is often used as a middle stage before final part manufacturing. The additive is mixed with a polymer using a specialty mixing extruder, producing a granulated material that is easier to handle and process. Depending on the formulation and intended use, the result may be a compound, a concentrate or a masterbatch.  

Common additives and fillers 

An additive is a functional ingredient added to a polymer to modify its properties. In the plastics industry, additives are commonly supplied in a masterbatchform. In everyday conversation, the word masterbatch is often omitted, which can cause confusion. Below is a list of some common additive types and reasons for their use: 

What is a concentrate?

A concentrate is a mixture containing a high level of one or more additives dispersed in a polymer.

In simple terms:

Concentrate = polymer + high amount of additive

For example:

Polypropylene carrier: 60% 
Carbon black: 40%

This could be described as a conductive concentrate. Concentrates are typically diluted with another polymer or base compound before the final product is manufactured.  

There are practical benefits. One concentrate can give the processor flexibility to create different formulations, for example by combining it with virgin or recycled polymer depending on the application. Transporting a concentrate instead of a ready-to-use compound can also simplify the logistics, i.e., easy to source materials can be purchased from more convenient locations, while the high value component comes in smaller or less frequent deliveries.  

What is a masterbatch?

This is the interesting part as masterbatch is the term more people are used to hearing. 

In practice, masterbatch and concentrate are often used as synonyms. The term masterbatch is commonly used for a highly loaded additive preparation that is added to another polymer, often at a very low dosage.

Color pigments and stabilizers are typical examples.

Conductive carbon black is a good example. Electrical conductivity requires sufficient carbon black in the final polymer. A reduction of only a few percentage points can have a significant effect on electrical performance. At the same time, there are practical limits to how much carbon black can be incorporated into the carrier while maintaining processability.

Color pigments behave differently. They can be effective at relatively low concentrations, and changing the dosage mainly affects the depth and coverage of the color.  

This is also why the terms masterbatch and concentrate do not always tell you enough on their own. The actual composition and recommended dosage are more useful when comparing materials. 

What are dosage and let-down ratio (LDR)? 

Both describe how much masterbatch or concentrate is used in the final formulation.

For example:

5 kg masterbatch + 95 kg natural polymer = 100 kg final material
The masterbatch dosage is 5%.

Let-down ratio can express the same formulation as a ratio:

LDR = Final Product Weight / Masterbatch Weight

In this example:

100 / 5 = 20:1

This means that 1 kg of masterbatch is used in 20 kg of final material: 1 kg masterbatch plus 19 kg of the other material.  

This also illustrates a potential problem with terminology. A ratio of 20:1 can be interpreted as 20 parts of one material plus one part of another. For practical discussions, it is often clearer simply to say:

5% masterbatch + 95% polymer 

What is dilution ratio? 

Dilution ratio is closely related to dosage and let-down rate, but the term is not always used in the same way.

In our example, the masterbatch represents 5% of the final compound and the natural polymer 95%. Depending on company terminology, dilution ratio and let-down rate may be used interchangeably.

Again, stating the actual percentages avoids ambiguity:

5% masterbatch + 95% polymer 
Clear and easy to understand.

5% DR / LDR or 20:1 LDR 
May require clarification about what the percentage or ratio refers to. 

Why final additive content matters 

Let's take the carbon black example one step further.

A concentrate contains:
40% carbon black + 60% polypropylene

If it is used at a dosage of 25%, the final carbon black content is:
25% × 40% = 10% carbon black

So:

Concentrate dosage = 25% equals 
carbon black content of 10%

This distinction matters when comparing different solutions. Two concentrates may have different additive loadings, recommended dosage levels, and prices per kilogram. Looking only at the price of the concentrate therefore does not tell you the actual material cost or whether the formulation will provide the required performance. 

Clear numbers avoid misunderstandings

The terminology around masterbatches and concentrates is widely used, but not always in the same way. That is not necessarily a problem. What matters is that everyone involved understands what the material contains and how it should be used.  Our recommendation is to keep it simple and refrain from using complex terminology but instead stick to expressions that cannot be misinterpreted. For example:

5% concentrate + 95% base polymer is obviously clearer than stating LDR 20:1