The safe application scope of inorganic low smoke zero halogen flame retardants needs to be comprehensively determined in combination with specific application scenarios, material systems and flame retardant types. Generally, the following conditions need to be met:
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First, core security indicators
Limiting Oxygen Index (LOI)
Standard requirements: Generally, it needs to reach 28%-35% or above (for example, the LOI of PP material with 50% aluminum hydroxide added can reach 30%).
Meaning: 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 performance.
UL-94 vertical burning grade
Standard requirements: It needs to reach grade V-0 (no dripping, no flame spread).
Application: Fire protection standards in fields such as electronics and electrical appliances, building materials, etc.
Heat release rate (HRR
The standard requirement is that the peak HRR should be reduced by more than 30% to 50%.
Meaning: Reduce the heat release during a fire and delay the spread of the fire.
Smoke density (SDR
Standard requirement: It should be lower than 150 (far lower than that of halogen-containing flame retardant materials).
Significance: Enhance the safety of personnel evacuation and rescue.
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Second, the key factors of the safe usage scope
Material system
Plastics such as PP, PE, EVA, etc., the amount of flame retardant added should be adjusted according to the characteristics of the base material (usually 40%-60%).
Rubber: such as EPDM, silicone rubber, etc., the compatibility between flame retardants and rubber needs to be considered.
Coatings: It is necessary to ensure the dispersion and stability of flame retardants in the coatings.
Type of flame retardant
Aluminum hydroxide (ATH) : Decomposition temperature 200-300℃, suitable for materials with lower processing temperatures.
Magnesium hydroxide (MDH) : Decomposition temperature 340-490℃, suitable for high-temperature processing materials.
Zinc borate (ZB) : It needs to be used in combination with phosphorus-based flame retardants to enhance carbonization.
Application scenarios
Wires and cables: They need to comply with the IEC 60332-3 standard to ensure that they do not drip or spread flames during combustion.
Building materials: They must meet the A-level fire protection standard (fire resistance limit >2 hours).
Electronic and electrical appliances: It is necessary to prevent the spread and dripping of flames to ensure the safety of the equipment.
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Third, specific suggestions on the scope of safe use
Addition amount control
Inorganic flame retardants: The usual addition amount is 40%-60%, and it needs to be adjusted according to the material properties and flame retardant requirements.
Synergistic flame retardant systems: such as the ATH+APP (ammonium polyphosphate) compound system, which can reduce the addition amount of a single flame retardant.
Processing temperature
ATH: The processing temperature should be below 200℃ to avoid decomposition and failure.
MDH: The processing temperature can reach over 300℃, making it suitable for high-temperature processing materials.
Environmental Protection and Toxicity
Inorganic flame retardants: They must comply with environmental protection standards such as RoHS and REACH to ensure they are non-toxic and harmless.
Combustion products: mainly water vapor and inorganic oxides, and the generation of toxic gases must be avoided.
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Fourth, verification methods for the scope of safe use
Laboratory test
LOI test: Determine the limiting oxygen index of the material.
UL-94 test: Verify the vertical burning grade of the material.
Cone calorimeter test: Evaluate the HRR and SDR of the material.
Practical application test
Simulated fire test: Verify the performance of materials in actual fires.
Long-term aging test: Evaluate the stability of flame retardants in materials.
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Fifth, Summary
The safe application scope of inorganic low smoke zero halogen flame retardants should be comprehensively determined based on the material system, the type of flame retardant and the application scenario. The key indicators include LOI, UL-94 grade, HRR, SDR, etc., which need to be verified through laboratory and practical application tests. Select the type and dosage of flame retardants reasonably to ensure that the materials not only meet the fire resistance performance requirements but also comply with environmental protection and safety standards.
