Since 1970
Since 1970
Carbon Black ASTM Grade N326 is a low-structure high-abrasion furnace (HAF-LS) black that provides high tear resistance, high tensile strength, and exceptional rubber-to-metal bonding properties. Due to its lower structure compared to standard N330, it delivers low compound viscosity, high loading capacity, and reduced heat buildup under dynamic strain. It is heavily utilized in steel-belted radial tire breaker/belt skim compounds, off-the-road (OTR) tires, and heavy-duty mechanical rubber goods.
Carbon Black ASTM Grade N326 belongs to the N300 series of furnace blacks characterized by medium-fine particle size (~26–30 nm) paired with a low structure (low oil absorption value). Under ASTM D1765 classification:
N indicates a normal curing rate.
3 designates the medium particle size range.
26 denotes its specific low-structure modification.
The key feature of N326 is its ability to impart high reinforcement and cut/chip resistance while maintaining superior green-tack and flexibility in unvulcanized rubber compounds.
Superior Rubber-to-Metal Adhesion: The preferred grade for steel-cord skim compounds because its lower structure enhances contact and chemical adhesion with brass-coated steel belts.
Low Heat Generation (Hysteresis): Exhibits low flex fatigue and reduced internal heat buildup under dynamic cyclic loading.
High Tear & Cut Resistance: Provides excellent resistance to chunking, tearing, and micro-cracking in severe off-road environments.
Easier Processing: Offers excellent flow behavior, reduced compound viscosity, and high loading capacity during mixing and extrusion.
| Property / Parameter | Typical Value | Unit | Test Standard |
| Appearance | Black Granular / Pellets | — | Visual |
| Iodine Adsorption Number | $82 \pm 5$ | g/kg | ASTM D1510 |
| Nitrogen Surface Area (NSA) | $78 \pm 5$ | $\text{m}^2/\text{g}$ | ASTM D6556 / D3037 |
| STSA (Statistical Thickness Surface Area) | $76 \pm 5$ | $\text{m}^2/\text{g}$ | ASTM D6556 |
| Oil Absorption Number (OAN / DBP) | $72 \pm 5$ | $\text{cm}^3/100\text{g}$ | ASTM D2414 |
| Compressed Sample OAN (COAN) | $68 \pm 5$ | $\text{cm}^3/100\text{g}$ | ASTM D3493 |
| Tinting Strength | $111 \pm 5$ | % | ASTM D3265 |
| Pour Density | $440 \pm 20$ | $\text{kg}/\text{m}^3$ | 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 |
Steel-Belted Radial Tires: Steel wire skim formulations for passenger car and commercial truck radial tires.
Off-The-Road (OTR) & Agricultural Tires: Treads and sidewalls requiring high resistance to rock cutting, tearing, and chipping.
Engine Mounts & Vibration Dampers: Industrial dynamic rubber parts needing low hysteresis and high fatigue resistance.
Conveyor Belting: Wire-reinforced belt covers and heavy-duty industrial hoses.