Inorganic Low Smoke Halogen Free Flame Retardants (Inorganic Low Smoke Halogen Free Flame Retardants) show significant advantages in fire protection performance by virtue of their unique chemical and physical properties. The following is a detailed analysis of its fire performance:
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First, the core mechanism of fire performance
Endothermic cooling effect
Typical substances: Aluminum hydroxide (ATH), magnesium hydroxide (MDH)
Principle: The decomposition absorbs a lot of heat during combustion (ATH decomposition absorbs about 1.97 kJ/g, MDH about 1.4 kJ/g), reduces the surface temperature of the material, and delays the combustion process.
Dilute the flammable gas
Decomposition products: water vapor, alumina/magnesium oxide
Action: Water vapor dilutes oxygen concentration, aluminum oxide/magnesium oxide coating insulates oxygen and inhibits combustion chain reaction.
Carbon formation and oxygen separation
Synergistic substances: zinc borate (ZB), phosphorus inorganic flame retardants (such as ammonium polyphosphate APP)
Principle: Promote the formation of a dense carbonized layer on the surface of the material, isolate heat and oxygen, and prevent the spread of flame.
Physical barrier action
Nanomaterials: nano silica, montmorillonite
Mechanism: Through the filling and dispersion of nanoparticles, the physical barrier properties of the material are enhanced and heat conduction is reduced.
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Second, key performance indicators
Limiting oxygen Index (LOI)
Typical value: After adding inorganic flame retardants, LOI can be increased from 21% to 28%-35% (such as the LOI of PP can reach 30% when ATH is added to 50%).
Significance: The higher the LOI value, the higher the oxygen concentration required for the material to maintain combustion in the air, and the stronger the fire resistance.
UL-94 vertical combustion rating
Effect: The material can achieve V-0 class (no dripping, no flame propagation), significantly better than non-flame retardant materials (usually V-2 class or no class).
Application: Meet the fire prevention standards of electronic appliances, building materials and other fields.
Heat release rate (HRR)
Reducing effect: It can reduce the peak HRR by 30%-50%, reduce the heat release during the fire, and delay the spread of the fire.
Smoke density (SDR)
Advantages: Low smoke generation during combustion (SDR value is usually less than 150, much lower than halogenated flame retardant materials), improve the safety of personnel evacuation and rescue.
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Third, fire performance in the application
Wire and cable
Effect: In the combustion test (such as IEC 60332-3), it can ensure that the cable does not burn in the flame, does not drip, and meets the low smoke halogen-free cable standard.
Case: In subway, high-speed rail and other rail transit, inorganic flame retardant cables can significantly reduce the risk of fire.
Building material
Effect: In the fire-proof board and insulation materials, the material can reach the A-level fire protection standard (fire resistance limit >2 hours).
Case: In high-rise building external wall insulation materials, inorganic flame retardants can prevent the spread of fire.
Electronic appliance
Effect: In the circuit board and shell material, it can prevent the flame from spreading and dripping, and protect the safety of the equipment.
Case: In the new energy vehicle battery pack, the inorganic flame retardant can withstand the high temperature when the battery is thermal out of control.
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Fourth, strategies to improve fire performance
Compounding technique
Methods: The inorganic flame retardants were combined with phosphorus and nitrogen flame retardants to form a cooperative flame retardancy system.
Effect: HRR and SDR can be significantly reduced, and LOI value can be increased.
Nano treatment
Methods: The particle size of flame retardant was reduced to nanometer level by nanotechnology.
Effect: improve the dispersion of flame retardant, enhance the carbonization and physical barrier effect.
Surface modification
Methods: The surface coating of flame retardant was applied to improve its compatibility with substrate.
Effect: Reduce the impact on the mechanical properties of the material, improve the flame retardant efficiency.
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Fifth, summary
Inorganic low-smoke halogen-free flame retardants have excellent fire performance by their multiple mechanisms such as heat absorption and cooling, gas dilution, carbon oxygen separation and physical barrier. Its environmental protection, low smoke, thermal stability and synergistic effects make it an ideal alternative to traditional halogenated flame retardants. In the fields of wire and cable, building materials, electronic and electrical appliances, inorganic flame retardants have shown significant application value, and their fire performance will be further improved with the advancement of technology in the future.
