Ammonium polyphosphate, abbreviated as APP, is a nitrogen-containing phosphate. Chemical formula H12N3PO4.The appearance of ammonium polyphosphate is a white powder, close to neutral, can be mixed with any other substances, but does not affect the chemical changes.
According to its polymerization degree, ammonium polyphosphate can be divided into three kinds of low, medium, and high polymerization. The greater the degree of polymerization, the less water soluble it is. When the degree of polymerization is below 20, it is called low-polymerization, which is water-soluble, and the degree of polymerization is above 50, which is called high-polymerization and can be used as a flame retardant.
The following are specific applications of ammonium polyphosphate.
Flame Retardants: APP is primarily used as a flame retardant in various industries. It can be incorporated into plastics, textiles, coatings, and foams to improve their fire resistance. APP releases ammonia when exposed to high temperatures, which dilutes flammable gases and inhibits combustion reactions.
Intumescent Coatings: APP is utilized in intumescent coatings, which provide passive fire protection for structural elements. When exposed to heat, these coatings swell, forming an insulating char layer that slows down the spread of fire and protects the underlying material.
Fireproofing Treatments: APP-based formulations are applied to fabrics, wood, paper, and other materials to impart flame retardant properties. This is commonly used in industries such as upholstery, furnishings, curtains, and building materials.
Adhesives and Sealants: APP can be added to adhesives and sealants to improve their fire resistance. This is particularly important in applications where these materials may be exposed to potentially flammable conditions.
Textile Processing: APP is employed in textile processing as a cross-linking agent or as a precursor for other flame-retardant finishes. It enhances the fire resistance of textiles without significantly affecting their physical properties.
Water-Based Systems: APP can be used in water-based systems, including paints, coatings, and emulsion polymers. It improves fire retardancy without negatively impacting the formulation's viscosity or stability.
Thermoplastics and Engineering Plastics: APP can be added to thermoplastic materials, such as polypropylene and polyethylene, to enhance their flame-retardant properties. It contributes to the reduction of smoke emission and helps prevent material dripping during combustion.
Fertilizers: In addition to its flame-retardant properties, APP is also used as a source of phosphorus and nitrogen in fertilizers. It provides essential nutrients to plants and helps promote growth and development.
Ammonium polyphosphate is an excellent raw material for the development of water-soluble fertilizers, which has the following advantages:
(1) High phosphorus nutrient content, nearly neutral pH, high safety factor for crop use.
(2) High solubility can be configured for liquid fertilizers with high phosphorus content; low crystallization temperature, easy to produce and use.
(3) Chelating effect on metal ions, can prevent the formation of precipitation of metal impurities in the solution, adding trace elements in liquid fertilizer, is conducive to making high concentration of high-quality liquid fertilizer. Phosphorus is not easily fixed by the iron, calcium, and other metal ions in the soil, but can instead form soluble complexes with the ineffective trace elements in the soil and be absorbed and used by plants.
(4) Although it is not directly absorbed by plants in the soil, it can be slowly hydrolyzed into orthophosphate in the soil and then used by plants, which is a slow-soluble and long-lasting fertilizer.
(5) It can be made into foliar fertilizer for foliar spraying of crops. Polyphosphate as a fertilizer can be applied at a dosage three times higher than orthophosphate, but it will not burn the leaves. Its neutral solution can be maintained on the foliage for several days without being evaporated or salted out.
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