Ammonium polyphosphate

Description

Ammonium polyphosphate (APP) is an organic salt of polyphosphoric acid and ammonia. As a chemical, it is non-toxic, environmentally friendly and halogen-free. It is most commonly used as a flame retardant, selection of the specific grade of ammonium polyphosphate can be  determined by the solubility, Phosphorus content, chain length and polymerization degree. The chain length (n) of this polymeric compound can be linear or branched. Depending on the polymerization degree, there are two main families of ammonium polyphosphate: Crystal phase I APP (or APP I), and Crystal phase II APP (or APP II).

1. APP phase I has a short and linear chain (n < 100), it is more water sensitive (hydrolysis) and less thermally stable; actually it begins to decompose at temperatures above 150 °C.
2. The second family of Ammonium polyphosphate is the APP Phase II; which has an high polymerization degree, with n>1000, its structure is cross linked (branched), and it is an high-quality non-halogenated flame retardant. APP phase II, Ammonium polyphosphate, has an higher thermal stability (the decomposition starts at approximately 300°C) and lower water solubility than APP I.

Uses

1. Ammonium polyphosphate is a specialty chemical that finds many different uses in key industries.  
2. Ammonium Polyphosphate, is an environment-friendly and halogen-free flame retardant. It is the main constituent of many intumescent flame retardant systems: coatings, paints and engineering plastics. It is used to prepare 20% Phosphorous/Nitrogen containing flame retardants, it can be used solely or in conjunction with other materials in the flameproof treatment for textiles, papers, fibers and woods. Special treatment can be used to prepare 50% high concentration flameproof formulations required for special applications.
3. The most common ammonium polyphosphate fertilizers have a N-P2O5-K2O (nitrogen, phosphorus and potassium) composition of 10-34-0 or 11-37-0. Polyphosphate fertilizers offer the advantage of a high nutrient content in a clear, crystal-free fluid that remains stable within a wide temperature range and stores well for long periods. A variety of other nutrients mix well with polyphosphate fertilizers, making them excellent carriers of micronutrients typically needed by plants.

Description

Ammonium polyphosphates are liquid fertilizers with compositions up to 11-37-0, manufactured by the reaction of anhydrous ammonia with superphosphoric acid. Superphosphoric acid is made by the concentration of regular wet-process acid up to P2O5 concentrations of 78%. Granular polyphosphates suitable for bulk blending are made by reacting ammonia with regular wet process acid of 52% P2O5 content and using the heat of reaction to drive off water to produce a phosphate melt of 10-43-0, with about 40% of the phosphorus in the polyphosphate form.

Agricultural Uses

Ammonium polyphosphate fertilizer is a unique liquid nitrogen-phosphorus fertilizer produced in Russia only by PhosAgro. Maximum phosphorus availability and absorption by plants compared to traditional solid phosphorus-based fertilizers, especially on soils with high calcium carbonate content. It ensures yield increase for different crops during foliar application. It is most effective in dry weather conditions. It is easy to store on farms.

Solubility in water

Ammonium polyphosphate (APP) is a branched or linear polymeric compound with a variable degree of polymerization (n). Generally, Ammonium polyphosphate of a low degree of polymerization (n ≤ 100, crystalline form I) is water soluble or water sensitive, while APP with longer chains (n ≥ 1000, crystalline form II) displays a very low water solubility (<0.1 g/100 mL). In general, long-chain APP starts to degrade at above 300°C, generating ammonia and polyphosphoric acid, while the short-chain one begins decomposing at 150°C.