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Carbon Black for Rubber Products

Carbon black for rubber products beyond tires: conveyor belts, hoses, seals, diaphragms, vibration mounts, bellows and rollers are all reinforced with it. Here, dimensional stability and extrusion behavior matter more than wear.

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Heavy black rubber conveyor belt passing through a vulcanizing press

Industrial rubber products (MRG, mechanical rubber goods) are the largest use of carbon black after tires. The selection criteria, however, differ markedly from tires: here the product is usually expected not to wear but to keep its shape, stay leak-tight and run for years without fatigue.

Product groups and key requirements

  • Conveyor belts: The cover rubber needs abrasion and tear resistance; the carcass needs dimensional stability. N220, N330 and N375 are common.
  • Hoses: Extrusion quality is decisive. High-structure soft grades (for example N550) provide a smooth surface and dimensional stability.
  • Seals and gaskets: Compression set is critical; medium-structure grades are preferred.
  • Brake diaphragms: N550 is the classic choice for fatigue resistance and dimensional stability.
  • Vibration mounts and bushings: Low hysteresis is required; high-surface-area grades are avoided.
  • Air springs, mudguards, wiper blades, conveyor rollers: Usually the N550 and N660 families.

Why soft grades dominate this sector

Thanks to their low surface area, soft grades (the N500 and N700 series) allow high filler and oil loadings in the compound. This both lowers cost and keeps die swell under control in extruded products. Their low heat build-up also extends the life of machine elements that run continuously.

SHP50: a specialty option for extrusion

As a medium-structure reinforcing grade, SHP50 offers higher jetness than N550 and relatively improved mechanical and abrasion properties. Thanks to its particle size distribution and balanced structure, it is preferred especially in extruded products and in pipe and profile production in the plastics sector.

What to Watch For in This Industry

Test compression set together with the grade

In seals and gaskets, a grade change can affect compression set more than expected; it must be measured before the formulation is approved.

Extrusion surface quality depends on structure

Grades with a high OAN give a smoother extrusion surface and less die swell. If you have surface defects, this is the first parameter to check.

High filler loading lowers cost, but there is a limit

Soft grades offer high loading capacity, but beyond a certain point elongation at break and fatigue resistance drop quickly. The limit differs for every formulation and needs trials.

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 N339 Hard grade N339 carbon black is a high-structure, high-modulus hard grade. It offers excellent… Iodine g/kg 90 ± 5 OAN ml/100g 120 ± 5 N326 Hard grade N326 carbon black is a low-structure, low-modulus hard grade with high elongation at… Iodine g/kg 82 ± 5 OAN ml/100g 72 ± 5 N234 Hard grade N234 carbon black combines high structure and high modulus. It delivers superior abrasion… Iodine g/kg 120 ± 5 OAN ml/100g 125 ± 5

Compare all grades

Trial program

1-pallet trial offer

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

How does it work?

Industry-Specific Questions

Which grade is used in conveyor belt production?

For abrasion resistance in the cover rubber, N220, N330 or N375; for dimensional stability in the carcass and intermediate layers, N550 or N660 are common. The operating environment (mining, cement, grain) and the abrasiveness of the conveyed material determine the choice.

Our hose extrusion has a poor surface. What should we do?

Usually a grade with a low structure (OAN) is being used, or dispersion is insufficient. Switching to a higher-structure soft grade (for example N550 instead of N772) or reviewing the mixing protocol may solve it.

Which grade is recommended for brake diaphragms?

N550 is the classic choice for this application: it offers low surface area, excellent dimensional stability and balanced dynamic properties.

Our vibration mounts are heating up.

A high-surface-area grade may be in use. In dynamic applications, hysteresis loss turns directly into heat; switching to a lower-surface-area grade markedly reduces heating.

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