Carbon black grades explained: N220, N330, N550, N660, N774
Buyer guide · Riddhi Polymers · Updated 2026-09-29
Short answer: In the ASTM system, the first digit after the N tells you the particle-size group: lower numbers mean finer particles, more reinforcement and abrasion resistance, but more heat build-up and harder mixing. N1xx–N3xx grades are used for tyre treads and wear-resistant parts; N5xx–N7xx grades for carcass, hoses, extrusions and general moulded goods; N990 as a low-reinforcing, easy-processing filler.
How to read a carbon black grade number
Grade names follow ASTM D1765. The letter N means normal cure rate (almost all rubber blacks). The first digit is the particle-size group; the last two digits distinguish grades within the group, mainly by structure (how the particles are aggregated).
| First digit | Typical particle size | Examples | Character |
|---|---|---|---|
| 1 | 11–19 nm | N110, N115 | Highest reinforcement and abrasion resistance |
| 2 | 20–25 nm | N220, N234 | Tread grades, high wear resistance |
| 3 | 26–30 nm | N326, N330, N339, N375 | All-round reinforcing grades |
| 5 | 40–48 nm | N550 | Smooth extrusion, good shape retention |
| 6 | 49–60 nm | N660 | General purpose, carcass and moulded goods |
| 7 | 61–100 nm | N762, N774 | Low heat build-up, high loadings |
| 9 | 201–500 nm | N990 | Thermal black, very easy processing, low reinforcement |
Common grades compared
| Grade | Typical iodine number (g/kg) | Where it is used |
|---|---|---|
| N220 | ~121 | Passenger and truck tyre treads, conveyor belt covers |
| N234 | ~120 | High-performance treads (higher structure than N220) |
| N330 | ~82 | Tyre carcass and sidewalls, belts, hoses, general reinforcement |
| N339 | ~90 | Treads needing a balance of wear and rolling resistance |
| N550 | ~43 | Extruded profiles, hoses, cable jackets, inner liners |
| N660 | ~36 | Carcass, inner tubes, moulded and extruded goods |
| N774 | ~29 | Moulded goods, mats, high-loading low-cost compounds |
| N990 | Very low | Seals and O-rings needing low hardness rise, FKM compounds |
Iodine numbers are typical target values from ASTM D1765 and indicate surface area; always check the batch COA for the actual figure.
How to choose
- Wear and tear matter most (treads, belt covers, rollers): N2xx or N3xx.
- Smooth extrusion and dimensional stability (profiles, hoses): N550.
- Low heat build-up and cost (carcass, moulded goods, mats): N660 or N774.
- Minimal reinforcement, easy flow (soft seals, FKM, high loadings): N990.
Finer blacks raise hardness, modulus and compound viscosity at the same loading, so switching grades usually needs a small oil or loading adjustment.
Frequently asked questions
Is N330 or N550 better for rubber hoses?
N550 is the usual choice for extruded hoses because it extrudes smoothly and holds shape; N330 is used where higher reinforcement or abrasion resistance is needed, for example in cover compounds.
What does the N in N330 mean?
N stands for normal cure rate under ASTM D1765. The first digit (3) is the particle-size group and the last two digits identify the specific grade.
Which carbon black gives the highest abrasion resistance?
The finest grades, N1xx and N2xx such as N110, N220 and N234, give the highest abrasion resistance and are used in tyre treads.
Related products and industries
- Carbon black supplier in Chennai
- Raw materials for tyre and tube manufacturers
- Raw materials for hoses, extrusions and moulded goods
Need help choosing a grade?
Riddhi Polymers has supplied rubber raw materials to 400+ manufacturers across South India since 2009. Tell us your application and we will suggest grades to trial. Request a quote, call +91 98418 19109 or email sales@riddhipolymers.com.
