Reinforcing Carbon Blacks
The highest volume use of carbon black is as a reinforcing filler in rubber products, especially tires. While a pure gum vulcanizate of styrene-butadiene has a tensile strength of no more than 2.5 MPa, and almost nonexistent abrasion resistance, compounding it with 50% of its weight of carbon black improves its tensile strength and wear resistance as shown in the below table. It is used often in the Aerospace industry in elastomers for aircraft vibration control components such as engine mounts.
| Name | Abbrev. | ASTM Desig. |
Particle Size nm |
Tensile Strength MPa |
Relative Laboratory Abrasion |
Relative Roadwear Abrasion |
|---|---|---|---|---|---|---|
| Super Abrasion Furnace | SAF | N110 | 20–25 | 25.2 | 1.35 | 1.25 |
| Intermediate SAF | ISAF | N220 | 24–33 | 23.1 | 1.25 | 1.15 |
| High Abrasion Furnace | HAF | N330 | 28–36 | 22.4 | 1.00 | 1.00 |
| Easy Processing Channel | EPC | N300 | 30–35 | 21.7 | 0.80 | 0.90 |
| Fast Extruding Furnace | FEF | N550 | 39–55 | 18.2 | 0.64 | 0.72 |
| High Modulus Furnace | HMF | N683 | 49–73 | 16.1 | 0.56 | 0.66 |
| Semi-Reinforcing Furnace | SRF | N770 | 70–96 | 14.7 | 0.48 | 0.60 |
| Fine Thermal | FT | N880 | 180–200 | 12.6 | 0.22 | -- |
| Medium Thermal | MT | N990 | 250–350 | 9.8 | 0.18 | -- |
Practically all rubber products where tensile and abrasion wear properties are crucial use carbon black, so they are black in color. Where physical properties are important but colors other than black are desired, such as white tennis shoes, precipitated or fumed silica has been used as a substitute for carbon black in reinforcing ability. Silica-based fillers are also gaining market share in automotive tires because they provide better trade-off for fuel efficiency and wet handling due to a lower rolling loss compared to carbon black-filled tires. Traditionally silica fillers had worse abrasion wear properties, but the technology has gradually improved to where they can match carbon black abrasion performance.
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