Applications of Inorganic Fillers in Fireproof Coating

As an important part of fire protection products, fire protection coatings can play a certain role in preventing fire accidents. Therefore, the fire safety accidents can be effectively reduced by improving the fire prevention performance of coatings.

One of the effective components of fire retardant coating is inorganic filler, which can not only improve the fire retardant performance of coating, but also reduce the production cost of coating. In addition, it also has the advantages of abundant raw materials, good thermal stability, non-toxic, etc., so it has been widely used in the field of fire retardant coatings and other industrial fields.

The scene of a fire accident
The scene of a fire accident

Flame retardant principle of inorganic filler

Inorganic filler can not only make fireproof coating decorative, but also can improve the mechanical and chemical properties of fireproof coating, as well as improve the heat resistance of coating and resistance to airflow impact. Different inorganic fillers have different working principles, which can be divided into the following categories.

  • Some inorganic filler melts can form a coating with the base material to isolate air and prevent combustion.
  • Some inorganic filler at high temperature will produce dehydration, decomposition and other endothermic reactions, or melting, evaporation and other endothermic processes, which will reduce the energy of the combustor and thus inhibit the combustion process.
  • The gas decomposed by the inorganic filler during combustion can dilute the concentration of combustible gas and oxygen and inhibit the combustion.

Common inorganic fillers

  • Aluminum hydroxide

As a flame retardant filler, aluminum hydroxide has the characteristics of good thermal stability, non-toxic, non-volatile, less smoke and good flame retardant effect, which is one of the most important inorganic fillers with three functions of flame retardant, smoke elimination and filling in fire retardant coatings.

Aluminum hydroxide will decompose and absorb heat when heated, and the water vapor generated after the reaction can reduce the concentration of combustible gas; In addition, alumina residue is deposited on the surface of the main material, which can isolate oxygen and inhibit combustion.

Aluminum hydroxide filler
Aluminum hydroxide filler
  • Magnesium hydroxide

Similar to aluminum hydroxide, magnesium hydroxide also has the above three functions. When heated, it will decompose to produce water, which takes away a lot of heat. At the same time, the release of steam can dilute the combustible gas around the matrix material to achieve the purpose of flame retardant. In addition, the decomposition of magnesium oxide will cover the surface of the substrate, which plays a role in oxygen isolation.

  • Talcum powder

The main composition of talcum powder is hydrated magnesium silicate, with fire resistance, acid resistance, insulation, chemical inertness, low cost, etc. When filled into the fire retardant coating, it can enhance the fire resistance of the coating and reduce the production cost of the coating.

  • Calcium carbonate

Due to the incombustibility of calcium carbonate and its decomposition into carbon dioxide at high temperature, the concentration of oxygen can be diluted to achieve the effect of combustion inhibition.

  • Kaolin

Kaolin can play the role of filling agent in fire retardant coatings. On the other hand, it can also improve the fire resistance of coating because of its good fire resistance.

  • Alumina

The melting point of alumina is as high as 2000 ℃. It has incombustibility itself, so it can effectively improve the fireproof performance of the coating when it is filled into the fireproof coating.

Comparison diagram of fireproof coating application
Comparison diagram of fireproof coating application
  • Nano titanium dioxide

Due to the advantages of three-dimensional mesh structure, large specific surface area, stable chemical structure, good dispersion and weather resistance, nano titanium dioxide can form mesh structure and dense carbonaceous layer when the coating is dry, which can improve the strength of the coating, ensure the physical stability of the medium, and enhance the fire resistance of the coating.

  • Titanium white

Titanium dioxide has good thermal stability and durability, with a melting point of 1800 ℃. Adding a certain proportion of titanium dioxide to the coating has a significant effect on improving the fireproof performance of the fireproof coating.

Growing trend

The addition of inorganic filler in the fire-resistant coating can effectively improve the fire-resistance performance of the coating, but inorganic filler also has some shortcomings, such as low adhesion with the substrate, easy to crack, powder, peeling and so on. Therefore, how to solve these problems, as well as the preparation of better performance of inorganic filler, are of great significance to the development of fire coatings and other industrial fields.

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