The application of Pigment Carbon Black in coatings is mainly in coatings for construction, automobiles, railway vehicles and ships, and it is also used as a toning pigment in gray and other color coatings.
Carbon Black has high blackness and tinting strength and stable price, so it is an indispensable black pigment in the paint industry. Most paints now use carbon black as a paint processing product.
Important index of pigment carbon black for coatings I: Blackness of Carbon Black
Blackness is the main indicator of carbon black used in coatings. When it is used in the coloring of black paints, such as black automotive topcoats, the higher the blackness of the carbon black used, the better.
When carbon black is used for toning, if the amount of melanin added is too high and too little, it is easy to cause color difference in different batches of paint products, so it is required to use carbon black with lower blackness.
Important indicator of pigment carbon black for coatings II: Tinting strength of carbon black
Tinting strength is the coloring ability of carbon black when white or colored pigments are mixed with carbon black. That is, the extent to which carbon black improves the light absorption of the mixture system.
This characteristic depends on the proportioning ratio of carbon black and pigment and the properties of carbon black itself. When the proportioning ratio is constant, the tinting ability of a certain carbon black is its tinting strength, which is called tinting strength in the coatings industry.
The carbon black particle size is small, the structure is low, and the coloring power is high. However, when the particle size is smaller than 20nm, the coloring power no longer increases, or even decreases.
Important indicators of carbon black for coatings III: The undertone/Hue of carbon black
The reduced light reflection of “carbon black particles” as particle size decreases also affects hue. Surface black coloring with fine particle size carbon black produces a bluish phase which further enhances the visual impression of high chroma. Pigmentation with coarse particle size carbon black produces a brown tint.
In addition to particle size, the structure of carbon black also has an impact on hue, with higher structured carbon blacks having a similar effect as coarser particle carbon blacks.
Pigment carbon black for coatings important index IV: The Gloss of carbon black
When the particle size of pigment carbon black is reduced or the structure is improved, the oil absorption of carbon black will increase, which will increase the viscosity of the coating.
Under the same concentration of carbon black, the free paint (film-forming substance) on the coating surface will decrease, so the gloss will decrease. .
When the oxygen-containing groups or volatiles on the surface increase, the wettability of carbon black in the binder will increase, the viscosity will decrease, the free paint on the coating surface will increase, and the gloss will increase.
Important indicators of pigment carbon black for coatings 5: Dispersion and stability of Carbon Black
The size of carbon black aggregates in paints is generally between 20 and hundreds of nanometers, and it is not easy to disperse in paints. The state of carbon black dispersed in paints has a great influence on the performance of paints.
In addition, when carbon black is used in coatings, especially when mixed with other pigments such as titanium dioxide, due to the difference in relative density, aggregate diameter, shape and surface chemistry, carbon black is prone to flocculation, which affects the dispersion and stability of coatings.
The paint processed with good pigment carbon black will have the following characteristics:
1. Optical properties such as blackness, tinting strength, gloss, hiding power, etc. are good.
2. Good liquidity
3. Good dispersion stability
4. The physical properties of the coating film such as smoothness, gloss retention, mechanical properties (hardness, elongation, impact strength and adhesion), and weather resistance are all improved.