How does Fire Degradation Occur in Paints?

Here are the three factors, resulting in fire degradation in paints:

1. Heat Breaks Chemical Bonds: When paint surfaces are exposed to fire, the temperature rises and causes structural changes in the paint film. Polymer cleavage occurs, which leads to fading and orange peels. Volatile organic compounds increase the fire flames and catch fire while evaporating.
2. Toxic Gas Formation and charring: Paint releases toxic gases such as carbon monoxide, hydrogen chloride, cyanide compounds, depending on their formulation. Smoke level rises and damages the paint. It leaves behind carbon residues and charring (black ashes) on the substrate.
3. Fire Triangle: Availability of specific environmental components increases combustion. The fire triangle is the chain reaction between fuel, heat, and oxygen. A paint is more fire sensitive when these three elements exist together. Industrial units with petroleum products and storage tanks catch fire without fire retardants. 

How Does Fire Retardant Paint Work?

Here are the four steps on how fire-resistant paints work:

1. Intumescent Reaction: Intumescent reaction occurs when the paint surface is exposed to harsh temperatures of 200 °C or above. Temperature and mineral acid act as an intumescent reaction stimulator. Blowing agents expand the intumescent material and form a thicker protective char layer. 
2. Thermal Barrier: Char layer protects the substrate from freeze-thaw cycles and prevent the substrate from melting. It does not allow the fuel to reside on the paint surface or ignite a fire. It disrupts the three-fire triangle mechanism and maintains the structural composition of the paint film.
3. Flame Inhibitors: Flame inhibitors increase the ability of paint to resist heat. Fire additives are classified into two categories depending on the Bromine and Chlorine elements. Halogen compounds contain Br and Cl elements, which release bromine atoms in the gas phase to disrupt the chemical reaction (flame). Alkyl halides, iodine monochloride (ICl), and table salt inhibit fire from spreading. The National Institute of Health reported that byproducts of halogen compounds (metal oxides, oxides) act as flame inhibitors at high temperatures. They added that hydrocarbons like methane and ethylene resist fire after reacting with H-atoms.

H + CH₄ → H₂ + CH₃

H + C₂H₄ → C₂H₅

They deactivate the H-atoms and produce an ethyl radical and methyl radicals. Unlike halogen compounds, halogen-free compounds do not contain Br and Cl elements. The most common halogen-free compounds are magnesium hydroxide, phosphorus, and melamine. They are expensive and do not produce any harmful smoke.

1. Smoke Suppression: Smoke suppressants like zinc borate, ammonium polyphosphate, and molybdenum compounds are used to limit toxic gases. They decrease the risk of shortness of breath when paints are exposed to fire. 

What are the Types of Fire Retardant Paint

Here are the five types of fire-retardant paint:

1. Intumescent Paint: Intumescent paint contains a binder (acrylic, chlorinated rubber), an acid source ( ammonium polyphosphate), a char former, pigments, and plasticizers to protect the substrate from flames. This paint layer expands to 50x when it faces extreme temperatures and weather changes. It is best for wood, steel, and metal items.
2. Cementitious Coating: Cementitious coating, also referred to as sprayed fire-resistant materials (SFRM), is a thick emulsion of cement, aggregates, and additives. Cement is also used as mortar to stick bricks. It binds the sand, polymer resins, and other additives to form a strong and hard paint emulsion. Cementitious coating is classified into three categories based on its ability to withstand fire and damage. Low-density coatings work well for low-traffic areas as they are not too strong to resist high flames. Medium-density cementitious coatings resist heat up to 100 °C. High-density coatings are used to paint industrial units and fireworks-producing companies as they are hard and fireproof. 
3. Fire-Resistant Latex Paint: Fire-resistant paints resist fire to some extent due to their low VOC content and water-based solvents. They cannot resist high temperatures like fireproof paints. Fire-resistant latex paints contain pentaerythritol, vinyl acetate latex, titanium dioxide, and additives in their formulation.
4. Two-Part Epoxy Fire Retardant Coating: Two-part epoxy fire-retardant coating consists of two components, A and B. First Component contains epoxy resins to bind, catalysts to initiate the reaction, carbon-forming agent to form char, and fireproof additives. Component B handles the curing process, which includes Curing Accelerator, pigment, and fillers. Epoxy coatings do not contain any solvent, Br, or Cl elements in their formulation. They do not release toxic smoke and VOC in the air that cause breathing problems. 
5. Clear Fire Retardant Coating: Clear fire retardant coating is used to protect the original color of the substrate from flames. It does not contain any pigments and comes crystal clear. Clear coatings are available as intumescent coatings and non-intumescent coatings to reduce the transmission of heat to the surface. They are used to paint wood surfaces that are near heaters, HVAC, or thermostats.

Where is Fire Retardant Paint Commonly Used?

Here are the six areas where fire retardant paint commonly used:

1. Commercial Buildings & Offices: Fire-retardant paint is used to paint walls (interior & exterior), ceilings, steel beams, wooden doors, trims, reception areas, electrical cable trays, and stairwells of commercial buildings. They are also used to paint wooden furniture like tables, chairs, stools, and desks to protect them from high heat.
2. Warehouses & Factories: Structural steel frameworks, storage racks, shelves, machinery, ceiling, roof panels, partition walls, and fire exits are painted with fireproof paints. It is also used on loading dock areas, wooden pallets, and crates.
3. Residential Homes: Fire-resistant paints are used to paint interior drywall and wooden roof trusses, ceilings, doors, wooden window frames, staircases, and wardrobes. Garage walls, attic, basements, outdoor wooden decks, and gas heater enclosures are also protected with these firprof paints.
4. Public Infrastructure: Fireproof paint is used on walls in schools, roofs of waiting areas, train or bus station walls, airport terminal walls, and libraries. They are applied on auditorium stages, backstage areas, fire exits, underground tunnels, and elevator areas
5. Marine & Offshore: Fire-resistant paint protects engine room walls, ceilings, bulkheads, and structural steel, storage compartments, cabin doors, stairwells, and deck ceilings from toxic smoke gases. Oil rigs, lifeboats, electrical cabinets, and control rooms are also painted to increase their lifespan.
6. Historic Buildings: Wooden floors, staircases, ceilings, windows, doors, heritage wall panels, and roof support pillars of historic buildings are painted with fire-retardant materials. It is also applied to antique wooden furniture like sofas, relaxing chairs, tables, and decorative items.

How to Know If Paint is Fire Retardant

Here are the four factors to check if your paint is fire-retardant:

1. Label & Technical Datasheet: Read the Material Safety Datasheet (MSDS), which is now called Safety Datasheet (SDS), and Technical Datasheet (TDS) to know the paint type in detail. TDS tells about technical specifications (drying time, curing time, density), application instructions, and performance data (durability, gloss). SDS informs about hazards, first-aid measures, physical properties, handling, and storage of paint cans. Look at the terms like ASTM E84, intumescent, class A, and fireproof for fire-retardant paints. 
2. Compliance & Certifications: Make sure that the paint manufacturing firm or cans comply with fire-resistant regulatory bodies. NFPA (National Fire Protection Association) has strict standards for fire-resistant paints, and BS 476 (British Standard 476) also verifies if the paint formulation meets the standards.  American Society for Testing and Materials (ASTM E119) is a test to check the ability of paint to resist extreme temperatures. Likewise, UL 263 (Underwriters Laboratories) also measures the ability of building materials to withstand high flames.
3. Manufacturer Claims: Verify the manufacturer claims with tests like the spectrophotometer, gloss meter, and abrasion testers, or other certifications. The manufacturer claims the durability, waterproofing, fire-resistance, coverage, and viscosity of paint under specific conditions and substrate. Make sure to validate fireproof claims under the mentioned temperature, surface, and square footage before taking any step.
4. Product Type & Usage Instructions: Fireproof paints have different types and usage methods.  They have three product types depending on the substrate, fire resistance, and application. Read the usage instructions, as fire-resistant paint requires a sealer or topcoat to reduce the level of flames.