How flame retardant coatings work?

What is flame retardant coatings?

Flame retardant coating, also known as fire-resistant coating is a specialized type of coating applied to surfaces of combustible substrate to improve their fire resistance and reduce their flammability. These coatings are designed to slow down or prevent the spread of flames when exposed to heat or fire. Flame retardant coatings have been widely used on various substrates, such as metallic materials, polymers, wood, and textiles. Flame retardant coatings are used in a wide range of applications and industries, mainly including building and construction, electronics, transportation, aerospace, textile and furniture.

 
The mechanism of flame retardant coatings.

1. Flame retardant coatings have non-flammable properties, which prevent the protected combustible substrate from directly contacting the air, thereby delaying the ignition time of the substrate.

2. The flame retardant coatings decompose and release inert gases when exposed to fire, diluting the combustible gases released from the protected substrate and the oxygen in the air, thus suppressing combustion.

3. Combustion is considered to be a chain reaction caused by free radicals. Flame retardant coatings containing nitrogen and phosphorus undergo thermal decomposition, releasing active free radical groups and combining them with organic free radicals to interrupt the chain reaction, thus reducing the combustion rate.

4. The intumescent flame retardant coating expands and foams when exposed to fire, forming a char layer, which is a solid, carbon-rich residue that acts as an insulating barrier, protecting the substrates beneath from the heat of the fire.

Classification of flame retardant coatings

Flame retardant coatings come in various types, here are several common classifications based on different elements:

1.According to the composition materials and dispersion systems of the coatings, it can be classified as：

Solvent-based and water-based flame retardant coatings.

2.According to the substrates applicable for flame retardant coatings, there are a few types below：

Steel structure, wood structure, cementitious concrete, and cable flame retardant coatings.

3. According to the shape of flame retardant coatings after being heated, there are two types:

Non-intumescent and intumescent flame retardant coatings.

 The fastest progress in flame retardant coating development has been in the field of intumescent emulsion-based formulations. Currently, these intumescent emulsion-type flame retardant coatings represent the most extensively used and manufactured type in China.

 
The types of flame retardant additive used in FR coatings.

Flame retardant coatings achieve fire-resistant effects mainly due to the presence or role of flame retardants in the coatings, therefore, In recent years, lots of flame retardant manufacturers have been committed to the R&D of different new flame retardants, so as to prepare ideal flame retardant coatings, some common types of flame retardants used in fire-resistant coatings include:

1. Halogen-Based Flame Retardants: While less environmentally friendly, halogen compounds such as bromine and chlorine have been used historically for their fire-retardant properties. They can disrupt the combustion process and create flame-inhibiting radicals. However, their use is decreasing due to environmental concerns.

2. Phosphorus and Nitrogen based Flame Retardants: 

2.1. Phosphorus compounds are widely used in fire-resistant coatings. They can work by forming a protective char layer, releasing fire-suppressing gases, and reducing the availability of flammable gases. Phosphorus-based flame retardants are often used in intumescent coatings.

2.2. Nitrogen compounds can inhibit the combustion process by releasing nitrogen gases that dilute the oxygen concentration around the fire. These flame retardants are commonly used in both intumescent and non-intumescent coatings.

In the past, It has been found that a single flame retardant mechanism makes it difficult to meet the flame retardant requirements of materials, that’s the reason why phosphorus-nitrogen composite flame retardants have been widely used in the field of polymer flame retardants in recent years.

 
3. Intumescent flame retardants

Intumescent flame retardant is a type of flame retardant additive that combines acid, carbon, and gas sources, which belongs to the phosphorus and nitrogen combined system. During the combustion process, they rapidly expand, so as to isolate oxygen and prevent heat transfer, and then achieve the purpose of flame retardant. Intumescent flame retardants are relatively stable and encompass various fire-retardant mechanisms. In recent years, they have seen increased application in fire-retardant coatings.

Mei Wang Chemical Range:

Mei Wang chemical is the global well-known producer of halogen-free intumescent flame retardants for fire-resistant coatings, we'd like to strongly recommend some of our core items for fireproof coatings, you can also visit the related product pages: https://www.mwchemical.com/product/coating-flame-retardant/

1.Mflam AP220, used as acid source. high cost-effective ratio ,mainly suitable for indoor usage.

1.2 Mflam AP220MF, enhanced with a coated surface treatment, which makes it more water-resistant and suitable for outdoor construction,

2.Mflam Penta M40, added in fire-resistant coatings as carbon source.

3.Mflam MA, used as gas source.


The effect show of Mflam intumescent flame retardant in painted wood.

For more information and technical support please contact our expert.

4. Graphene and Nanomaterials: Emerging technologies are exploring the use of nanomaterials like graphene to enhance fire-resistant coatings. These materials can form barrier layers and prevent heat transfer, effectively reducing the spread of flames.

5. Others : Inorganic fillers like aluminum hydroxide, magnesium hydroxide, and clay are often used as flame retardants. These fillers release water vapor when heated, cooling down the material and diluting flammable gases. Silicon and inorganic silicon flame retardant.

Usually, these flame retardants should be combined with other flame retardants and synergists in order to achieve good flame retardant effect in coatings.

Conclusion:

The choice of flame retardant depends on factors such as the application, the substrate material, environmental considerations, and regulatory requirements. The goal is to achieve the desired level of fire protection while taking into account safety, performance, and sustainability aspects.