Ammonium Polyphosphate (APP) is a 100% water soluble phosphate and it is mostly utilized in plants. APP is an inorganic salt of ammonia and polyphosphoric acid, whose chain length is both variable and branched. Short length chain of APP are very much water sensitive and unstable compared to longer chain APP. There are two main families of APP Crystal Phase 1 APP (Linear structure) and Crystal Phase 11 APP (Branched structure). APP is non-toxic, environmentally friendly material and it is used as flame retardant as it does not generate smoke due to the unique mechanism of Intumescence
APP is prepared by reaction between concentrated phosphoric acid with ammonia. However, impurities consisting of iron and aluminium are soluble in concentrated phosphoric acid which forms gelatinous precipitates in APP.
In industrials, APP is manufactured by polycondensation between monoammonium phosphate and urea.
APP is a very efficient halogen free flame retardant mainly used in polyolefin (PE, PP), thermoset resins such as epoxy resins, and polyurethane, unsaturated polyester phenolic resins. It is an intumescent flame-retardant component for coating, wood, paper, plywood, cable, fibre, plastic, rubber, and resin, component of fire-extinguishing dry-powder for fire of forest, oil-well, and coal mine.
APP is used as a fertilizer for many crops as it is a rich source of phosphorus and nitrogen. The ratio of N2:P2O5 is suitable for many crops, and this combination improves the plant nutrient intake and let the plant utilize the phosphorus more efficiently. APP contains polyphosphates which extracts micronutrients in solution, aiding in the uptake of micronutrients and hence, making them easily available for plant.
APP is also used as food additive and emulsifier. It is also used as a nutrient for yeast and increases the water binding properties. It is mainly used in processed cheese and frozen poultry.