Carbon Black ASTM Grade N550
Carbon Black ASTM Grade N550

Carbon Black ASTM Grade N550

Carbon Black ASTM Grade N550 is a fast-extruding furnace (FEF) black characterized by medium surface area and high structure. It imparts smooth extrusion surfaces, high green strength, high modulus, and low die swell to uncured rubber compounds. Widely recognized as a semi-reinforcing grade, N550 is extensively used in tire carcass and sidewall compounds, extruded rubber profiles, hose inner tubes, weatherstripping, and cable jacketing.

Available Grades
N220 N326 N330 N550 N660 N774
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Overview & Classification

Carbon Black ASTM Grade N550 belongs to the N500 series of furnace blacks characterized by medium particle size (~39–55 nm) combined with a high structure (high oil absorption number). Under ASTM D1765 classification:

  • N indicates a normal curing rate.

  • 5 designates the medium-coarse particle size group.

  • 50 denotes its specific high-structure, fast-extruding character.

Because of its high structure relative to its surface area, N550 provides high dimensional stability and excellent processing behavior without over-thickening the compound.

Performance Characteristics

  • Fast Extrusion & Smooth Surface Finish: Significantly reduces die swell and surface roughness during extrusion, enabling high-speed processing of profiles and tubes.

  • High Green Strength & Stiffness: Gives uncured rubber high resistance to deformation during handling and molding.

  • Low Heat Generation: Generates low internal heat buildup (hysteresis) and excellent dynamic resilience under cyclic stress.

  • Moderate Reinforcement: Offers medium tensile strength and tear resistance, making it ideal for non-tread parts where extreme abrasion resistance is not required.

Typical Technical Specifications

Property / Parameter Typical Value Unit Test Standard
Appearance Black Granular / Pellets — Visual
Iodine Adsorption Number $43 \pm 4$ g/kg ASTM D1510
Nitrogen Surface Area (NSA) $40 \pm 4$ $\text{m}^2/\text{g}$ ASTM D6556 / D3037
STSA (Statistical Thickness Surface Area) $39 \pm 4$ $\text{m}^2/\text{g}$ ASTM D6556
Oil Absorption Number (OAN / DBP) $121 \pm 5$ $\text{cm}^3/100\text{g}$ ASTM D2414
Compressed Sample OAN (COAN) $85 \pm 5$ $\text{cm}^3/100\text{g}$ ASTM D3493
Tinting Strength $55 \pm 5$ % ASTM D3265
Pour Density $360 \pm 20$ $\text{kg}/\text{m}^3$ ASTM D1513
Heating Loss (Moisture) $\le 1.5$ % ASTM D1509
Ash Content $\le 0.5$ % ASTM D1506
45 $\mu\text{m}$ Sieve Residue $\le 0.1$ % ASTM D1514

Primary Applications

  1. Tire Components: Tire sidewalls, carcass plies, apex, inner liners, and tube compounds.

  2. Extruded Profiles & Seals: Automotive weatherstripping, window channels, door seals, and extruded gaskets.

  3. Hoses & Tubing: Hydraulic hose inner tubes, automotive cooling hoses, and fuel line covers.

  4. Mechanical Rubber Goods (MRG): Engine mounts, rubber bushings, conveyor belt friction layers, and wire jacketing.