Flame retardant masterbatch works by adding chemicals to plastic that interfere with the combustion process. These chemicals act in one of four ways: by cooling the material (endothermic reaction and release of water), by forming a protective char layer that acts as a barrier to oxygen and heat, by releasing inert gases (like hydrogen halide gas) that dilute oxygen and suppress flames, or by chemically interfering with the gaseous phase reactions necessary for fire to spread. These mechanisms slow down or stop the spread of fire, helping plastic products meet safety standards.
1. Composition
A flame retardant masterbatch is a concentrated blend of flame retardant additives dispersed in a polymer carrier (like polyethylene or polypropylene). The additives can be:
- Halogenated compounds (e.g., brominated or chlorinated)
- Non-halogenated compounds (e.g., phosphates, aluminum hydroxide, magnesium hydroxide)
- Synergists (like antimony trioxide) that enhance effectiveness
2. Mechanism of Action
Flame retardants can work through several mechanisms depending on the type:
a) Gas Phase Action
- Some additives release inert gases (like water vapor, CO₂, or halogen radicals) when heated.
- These gases dilute flammable gases around the polymer and interrupt the combustion chain reaction, reducing flame spread.
b) Condensed Phase Action
- Certain flame retardants form a protective char layer on the polymer surface when exposed to heat.
- The char acts as a thermal barrier, slowing heat transfer and protecting underlying material from igniting.
c) Endothermic Reaction
- Some additives (like aluminum hydroxide or magnesium hydroxide) absorb heat as they decompose, lowering the temperature of the plastic and delaying ignition.
3. Benefits
- Reduces the risk of fire and smoke generation.
- Helps meet fire safety standards (UL 94, ASTM, EN 13501, etc.).
- Can be used in electrical, construction, automotive, and household applications where fire resistance is crucial.
4. Application
The masterbatch is mixed with base polymers during extrusion or molding. Its concentrated form ensures even dispersion of flame retardants throughout the plastic, providing consistent fire-resistant properties.
In short, flame retardant masterbatches chemically and physically interfere with combustion—either by cooling, forming a protective layer, or disrupting the flame’s chemical reaction—while being easy to incorporate into standard plastic processing.