Ammonium Polyphosphate (APP) is not a single substance, but a large “family,” with performance differences primarily determined by two dimensions: degree of polymerization (n-value) and crystal structure.
Classified by degree of polymerization:
- Low-polymer APP (n=10~20): High water solubility, poor thermal stability, mainly used in fire extinguishing agents, paper flame retardants, or as slow-release fertilizers.
- High-polymer APP (n>20): Low water solubility, good thermal stability, the mainstay of industrial flame retardants in plastics, coatings, etc.
- Ultra-high degree of polymerization APP (n>1000): Almost insoluble in water, decomposition temperature can reach above 350℃, specifically used in high-end engineering plastics and high-temperature applications.
According to crystal form:
- Type I APP: Mostly amorphous, highly hygroscopic, and prone to agglomeration, suitable for low-end applications where water resistance requirements are not high.
- Type II APP: Crystalline, with excellent hydrolysis resistance and thermal stability, it is the current mainstream choice in industry and is widely used in high-performance flame-retardant materials.
This refined classification system allows APP to accurately match the needs of different application scenarios.
APP stands out in the flame retardant market due to its comprehensive and balanced performance. Its core advantages can be summarized in four points:
First, excellent environmental friendliness. APP is halogen-free and does not release toxic hydrogen halide gases when burning, complying with international environmental standards such as RoHS and REACH, making it an ideal alternative to traditional brominated flame retardants.
Second, high flame retardant efficiency. Adding 5%-25% to plastics can achieve the highest UL-94 V-0 flame retardant rating, meaning the material extinguishes immediately upon removal of the flame and exhibits no dripping.
Third, strong processing adaptability. Type II APP has an initial decomposition temperature ≥260℃, far exceeding the processing temperature of common engineering plastics such as PP and PA, ensuring stability and non-decomposition during injection molding and extrusion.
Fourth, excellent smoke suppression. It produces very little smoke during combustion, preventing secondary harm, which is especially important in confined spaces such as subways and tunnels.
Compared to traditional flame retardants, APP’s advantages are obvious. Compared to halogenated flame retardants, it is more environmentally friendly; compared to aluminum hydroxide (ATH), it has a better flame retardant effect at the same addition amount, and the decomposition temperature of ATH is only about 180℃, which limits its application in high-temperature processed materials.
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Post time: Aug-26-2026
