How to check the blackness of pigment carbon black

black is a vital pigment used across various industries, including coatings, inks, and plastics. Its performance is determined by several key factors, including blackness, structure, pH, and dispersion. This article delves into these aspects to provide a comprehensive understanding of carbon black's properties and how to optimize its use.

Blackness and Particle Size

Blackness is a crucial indicator of carbon black's quality. Although structure and surface chemistry influence blackness to some extent, the average particle size of carbon black has a more direct correlation. Finer particles absorb more light, resulting in higher blackness. However, as particle size decreases, surface area increases, leading to higher viscosity and thixotropy in the base material system. Carbon black's hygroscopic nature, influenced by its large surface area, necessitates special packaging, storage, and transportation measures to minimize moisture absorption, which can complicate processing.

Particle Size and Properties

As particle size decreases or surface area increases, blackness and viscosity rise, while dispersibility and gloss decrease. Conversely, increasing structure (more chain branches) enhances blackness and gloss but also increases viscosity and dispersibility. Acid value also plays a role: higher acid values correlate with increased blackness, dispersibility, and gloss, but decreased viscosity.

Structure and Dispersion

Structure refers to the morphology of carbon black aggregates. Higher structure (more chain branches) typically indicates a more complex aggregate shape, while lower structure suggests a simpler, more spherical shape. Low-structure carbon black offers stronger coloring power, better brightness, and superior blackness but is more challenging to disperse. High-performance dispersants are essential for achieving optimal dispersion, especially with high-pigment carbon black. Inadequate dispersant selection, insufficient dosage, or incompatibility with the resin system can lead to flocculation of dispersed pigment particles, compromising blackness.

pH and Surface Chemistry

pH is a critical indicator of carbon black's surface oxidation level. The oxygen content and surface acidic oxygen groups determine its surface chemistry. Furnace black typically has fewer surface functional groups and a small amount of soluble salts, resulting in a neutral or weakly alkaline nature. Surface oxidation treatments can alter the number of functional groups, making the pH acidic and improving dispersion performance, viscosity, stability, and flowability.

Achieving Optimal Blackness and Hue

To accurately compare carbon black's blackness and hue, complete dispersion is essential. Poor resin wetting or incorrect dispersant selection can hinder the full expression of carbon black's properties. High-pigment carbon black, in particular, requires appropriate dispersants and optimal dosages to prevent flocculation and ensure accurate blackness assessment.

In conclusion, understanding and optimizing carbon black's blackness, structure, pH, and dispersion are crucial for achieving superior performance in various applications. By selecting the right carbon black grade, dispersant, and processing conditions, manufacturers can unlock the full potential of this versatile pigment.