Pigment carbon black is the dominant black colorant for coatings, printing inks and plastics industries. Compared with traditional black pigments such as bone black, graphite, iron oxide black and aniline black, it boasts outstanding comprehensive advantages: long-term color stability, resistance to various solvents, resistance to acid and alkali corrosion, and excellent heat resistance without discoloration at high temperatures, making it compatible with most industrial coloring systems. The final application performance of carbon black is entirely determined by three core physical properties and surface modification processes.

Carbon black can undergo oxidative surface modification before delivery. By regulating oxygen-containing functional groups on particle surfaces, the surface polarity of carbon black is adjusted to fit different carrier systems including water-based, solvent-based, powder and plastic systems. This treatment greatly improves the wettability and long-term dispersion stability of pigments in resins, and enables precise control over finished product jetness, undertone and system fluidity. Volatile content acts as a key indicator for modification. When the volatile content is below 4%, carbon black features minimal grinding resistance, delivering optimal dispersion and fluidity in coatings and ink systems.

Particle size and specific surface area exert a direct impact on finished product performance. Smaller particle size and larger specific surface area deliver superior jetness and coloring strength, yet come with higher dispersion difficulty, increased oil absorption and poorer system fluidity. Larger particle size and smaller specific surface area result in easy grinding and dispersion, low oil absorption and low dosage requirements for better construction fluidity, at the cost of slightly reduced jetness and coloring strength. There is a critical threshold: when the particle size is less than 16 nm, carbon black is easily covered by white fillers, raising the transparency of paint films and ink films and reducing coloring strength instead. In light-tone systems, small-particle carbon black scatters short-wavelength light and produces a red undertone, while large-particle carbon black scatters long-wavelength light and delivers a pure blue undertone. Blue pigments can be blended to correct red undertone defects if they occur.

Carbon black structure is represented by the DBP oil absorption number, where the structure level reflects the size of three-dimensional aggregates formed by the fusion of carbon black particles. Low-structure carbon black contains few internal voids and does not absorb excessive resin or solvent, resulting in low system viscosity and excellent fluidity. The ink industry universally prefers low-structure products with a DBP oil absorption value ranging from 45 to 120ml/100g. High-structure carbon black disperses faster and delivers higher gloss on paint and ink films, yet it tends to form a network structure within binders that encapsulates large amounts of resin, leading to elevated system viscosity and increased thixotropy.

The surface of carbon black contains oxygen-containing groups including hydroxyl, quinone and lactone groups, which constitute the volatile fraction. These functional groups work similarly to wetting and dispersing agents. During grinding and processing, they mitigate particle agglomeration, cut production energy consumption, improve system fluidity, reduce thixotropy and yield value, and minimize product defects such as floating, flocculation and sedimentation.