Phosphorus-Based Mechanism: Red phosphorus is a highly effective flame retardant that works by promoting the formation of a protective ｃｈａｒ layer when exposed to heat. The phosphorus compounds released during decomposition help to suppress combustion and slow the spread of fire.
Endothermic Decomposition: Upon heating, red phosphorus decomposes endothermically, absorbing heat and thus lowering the temperature of the material, which reduces the intensity of flames.
Formation of a Protective ｃｈａｒ: Red phosphorus encourages the formation of a stable ｃｈａｒ layer that insulates the material from heat and flames, preventing further combustion and extending the material's flame resistance.
Advantages:
Highly Effective at Low Loadings: Red phosphorus provides exceptional flame retardancy even at relatively low concentrations, making it cost-effective for a wide range of applications.
Halogen-Free & Non-Toxic: As an inorganic flame retardant, red phosphorus is free of halogens, offering a safer, non-toxic alternative to halogenated flame retardants.
Thermal Stability: Red phosphorus is stable at high temperatures and is effective in materials exposed to heat during processing or service conditions.
Low Smoke Generation: Red phosphorus reduces the amount of smoke and toxic gases emitted during combustion, which enhances the safety of products containing it.
Applications:
Plastics & Polymers: Widely used in polyamides (PA), polyester, and engineering plastics, including polycarbonate (PC) and ABS, for improved flame retardancy.
Electrical & Electronics: Used in wires, cables, connectors, and circuit boards to provide electrical insulation with enhanced fire safety.
Coatings & Paints: Used in fire-resistant coatings for building materials, machinery, and transportation equipment.
Automotive: Added to automotive components, including interior parts and under-the-hood components, for flame retardancy and safety.
Rubber & Elastomers: Provides flame resistance in rubber compounds for automotive, industrial, and construction applications.
Processing Considerations:
Compatibility: Red phosphorus can be used with a variety of polymers, including polyamides, polycarbonates, and styrenics. However, it may require proper dispersion techniques due to its tendency to agglomerate.
Loading Levels: Typically used at 2–10% loading depending on the material and required level of flame resistance. Higher loading may be needed for more challenging applications.
Handling & Safety: Red phosphorus is highly reactive and must be handled with care. It should be stored in a dry, well-ventilated area, and proper protective equipment should be worn to avoid exposure to dust or fumes.
Limitations:
Impact on Material Properties: High loading of red phosphorus may affect the mechanical properties of the polymer, such as flexibility or strength.
Potential for Toxicity: Although red phosphorus is considered non-toxic, its handling requires caution due to its reactivity and the possibility of releasing toxic phosphorus compounds under certain conditions.
