It is understood that ammonium polyphosphate, also known as ammonium polyphosphate (APP for short), is a white powder and is a nitrogen-containing phosphate that is nearly neutral. , good dispersion and no reaction with other substances. Good thermal stability, decomposition temperature is not lower than 250℃. Ammonium polyphosphate can be divided into three types according to its degree of polymerization: oligopolymer, medium polyphosphate, and high polymer. The greater the degree of polymerization, the smaller the water solubility. Crystalline ammonium polyphosphate is a water-insoluble and long-chain polyphosphate. There are five variants from I to V. Among them, high-polymerization crystalline type II ammonium polyphosphate has significant advantages in the field of polymer materials due to its good water insolubility, high decomposition temperature, and good compatibility with polymer materials. Compared with halogen-containing flame retardants, crystalline type II ammonium polyphosphate has the characteristics of low toxicity, low smoke, and inorganic. It is a new type of high-efficiency inorganic flame retardant.
The application and role of ammonium polyphosphate in fiber products:
Flame retardants based on ammonium polyphosphate (APP) are used in The phosphoric acid decomposed at high temperature interacts with the hydroxyl groups in cellulose to produce phosphate ester and water, which dehydrates and carbonizes fiber products. On the one hand, the carbonized layer blocks heat conduction, and on the other hand, the polyphosphoric acid decomposed into glassy form also acts as heat insulation and It blocks oxygen, thereby inhibiting the burning of the substrate.
A certain research institute used an aqueous transparent flame retardant based on ammonium polyphosphate (APP) to treat pure cotton fabrics with an oxygen index of 50%. When manufacturing fibers, the fiber sheets made by adding 25% APP and 1% aluminum sulfate have reached JIS-AI321 flame retardant level 3.
The application and role of ammonium polyphosphate in coatings:
The intumescent fire retardant coating formulated with ammonium polyphosphate (APP) has excellent flame retardancy. It has the characteristics of longer flame retardant time than fire retardant coatings formulated with ammonium orthophosphate and ammonium metaphosphate, good detachability, and little change in the coating in a humid environment or after being soaked in water.
Ammonium polyphosphate (APP) is both a flame retardant and a foaming agent in the coating. After reaching a certain temperature, ammonium polyphosphate (APP) decomposes to generate phosphoric acid and ammonia, which dilute and isolate the air. At the same time, phosphoric acid and pentaerythritol generate ester compounds that cover the surface of the substrate and retard combustion.
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