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Carbon Black for Masterbatch and Plastics

In black masterbatch production, carbon black is both a pigment and a UV protector, so choosing carbon black for masterbatch is about jetness, ease of dispersion and UV resistance rather than abrasion. PE wax is the carrier that makes dispersion possible.

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Black masterbatch granules flowing into a collection bin at the extruder outlet

The plastics sector is the largest use of carbon black outside tires. Its function here is entirely different, however: in plastics, carbon black is not a reinforcing agent but a pigment and UV stabilizer.

How black masterbatch works

Carbon black is not mixed directly into the plastic resin. It is first dispersed at high concentration (typically 20–50%) in a carrier polymer to produce a masterbatch, which is then added to the main resin at a low ratio (1–5%). The reason for this two-step method is dispersion: carbon black particles have a strong tendency to agglomerate and stay in lumps when mixed in directly.

The role of PE wax

Polyethylene wax is used as a dispersion aid in masterbatch production. Its low melt viscosity lets it wet carbon black agglomerates, its lubricating effect reduces friction and therefore temperature in the extruder, and it allows higher pigment loadings. Oxidized PE wax types are preferred especially in highly filled formulations, because they are more compatible with pigments that have polar surfaces.

How to choose the right grade

  • Jetness and undertone: Small-particle grades (high iodine adsorption) give a deeper black with a blue undertone; coarse-particle grades produce a brownish undertone.
  • UV protection: Effective UV protection requires a small particle size (about 15–25 nm) and very good dispersion. Poorly dispersed carbon black does not provide UV protection.
  • Ease of dispersion: High-structure grades disperse more easily; low-structure grades need higher shear.
  • Cost: For coloring applications, soft grades such as N550, N660 and N772 give sufficient results at lower cost.

Applications

Black masterbatch is used across a wide range, from film and bag production to injection molding, and from pipe and profile extrusion to automotive interior and exterior parts. Agricultural mulch films, garbage bags, irrigation pipes and cable jackets are the highest-volume applications.

What to Watch For in This Industry

UV protection depends on dispersion, not dosage

3% of poorly dispersed carbon black gives weaker UV protection than 2% of well-dispersed carbon black. The pressure filter value test is the most practical way to measure dispersion quality.

Moisture causes bubbles in masterbatch production

The heating loss of carbon black (ASTM D1509) should be low, and the material should be stored dry. Dry it before extrusion if necessary.

Too much PE wax lowers mechanical values

Wax improves dispersion, but when overused it weakens tensile strength and adhesion properties in the end product. The typical dosage is 2–5% in the masterbatch.

N330 Hard grade N330 carbon black is the most widely used general-purpose grade in the industry. It… Iodine g/kg 82 ± 5 OAN ml/100g 102 ± 5 N375 Hard grade N375 carbon black has a lower structure than N339 and offers excellent processing and… Iodine g/kg 90 ± 5 OAN ml/100g 114 ± 5 N550 Soft grade N550 carbon black is a low-surface-area carcass grade. It gives rubber compounds… Iodine g/kg 43 ± 5 OAN ml/100g 121 ± 5 N660 Soft grade N660 carbon black has a lower surface area than N550 and a medium-low structure. It keeps… Iodine g/kg 36 ± 5 OAN ml/100g 90 ± 5

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Trial program

1-pallet trial offer

Test the product and return it if you are not satisfied. No obligation.

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Industry-Specific Questions

Which carbon black grade is suitable for masterbatch production?

For coloring-focused applications, N550, N660 and N772 are economical, easily dispersed options. For applications that need high jetness, a deep tone and strong UV protection, smaller-particle grades are preferred. SHP50 is an intermediate option because it offers higher jetness than N550.

Can't I use a black pigment instead of carbon black?

Organic black pigments do not match the UV protection and thermal stability of carbon black, and they cost far more. In plastics, carbon black has no practical alternative.

What dosage of PE wax should be used?

In masterbatch formulations, the typical dosage is 2–5% and increases with pigment loading. The exact level is set by trials according to the carrier resin and extruder type.

What is the difference between oxidized and non-oxidized PE wax?

Oxidized types have carboxyl groups added to the molecular chain; this polarity gives better interaction with the pigment surface and easier dispersion. Non-oxidized types offer a pure lubricating effect and higher water repellency.

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