– Aug 21, 2020
(Source from: SpecialChem.com)
As I write this article, I can hear an aircraft flying overhead fighting an 11,000-hectare wildfire near my Southern California home. These converted civilian and military airplanes and helicopters, drop water and fire-retardant solutions on wildfires in canyons and atop mountains which are otherwise inaccessible.
Fire retardants moderate the spread of wildfires by acting as a temporary coating for nearby fuels. Often brightly colored to show the pilots where the flame retardants have been applied, they are a valuable tool in the fight to save lives, homes and forestlands.
Heat resistant and flame-retardant coatings can protect materials from damage due to high temperatures and fire. The two types function very differently, even though they might seem to be the same.
- Heat resistant coatings protect a surface for prolonged periods at elevated temperatures. This protection might be from corrosion or chemical attack, such as an interior pipeline coating.
- Flame retardant coatings, on the other hand, prevent the fire from spreading and/or prevent catastrophic damage to the coated object.
While heat resistant coatings are designed for use under the normal service conditions of the intended application, flame retardant coatings are designed to protect under extreme conditions.
Let’s review the types of heat resistant and flame retardant coatings along with their recent developments in detail.
Airplanes Dropping Fire-Retardant Solutions on Wildfires
(Credits: Luis Sinco for the Los Angeles Times)
Heat Resistant Coatings
If a coating remains unaffected by elevated temperatures, it can be called a heat resistant. Heat resistant coatings protect components exposed to extreme temperatures or temperature fluctuations. Formulating coatings which continue to fulfill their intended protective function when exposed to prolonged heat or extreme temperature changes is challenging.
Types of Heat Resistant Coatings
The different types of heat resistance coatings include epoxy and silicone, ceramic, powder coatings, etc.
Epoxy and Silicone Coatings
Epoxy and silicone-based coatings offer a medium to high-temperature protection in combination with the corrosion
and chemical resistance
expected of this family of protective coatings.
Silicone and organo-silicone coatings are widely used for their broad utility as heat resistant coatings and for their ability to be formulated to achieve a price/performance balance. While pure silicone coatings are expensive silicone resins can be blended with other binders, such as epoxies
to improve the heat resistance of the lower cost base polymer.
Metal Additive Coatings
When corrosion resistance and the ability to withstand service temperatures above 400°C are required, metal pigments are often utilized in the coating. Leafing aluminum pigments are widely used in these applications, often combined with silicone or epoxy resins.
provide a hard finish with corrosion and chemical resistance at temperatures exceeding 590°C. These are often applied as so-called burn off coatings.
A coating containing an organic binder and ceramic components is applied to the surface and cured at a temperature below the ultimate service temperature. While the coated object is reaching the surface temperature, the organic binder burns off, leaving a ceramic coating on the surface.
Depending on the powder coating type, they can resist temperatures between 200 and 550°C. Heat resistant powder coatings are often used on consumer products which reach high temperatures during use, such as:
- Ovens, and
- Barbecue grills