Фосфит алюминия

Description

Aluminum phosphite is an inorganic salt of phosphorous acid and aluminum, gross formula AlO3P. Belongs to the class of phosphorus-containing aluminum compounds used as halogen-free flame retardants and polymer stabilizers. Unlike aluminum phosphate, where phosphorus is in the +5 oxidation state, aluminum phosphite contains trivalent phosphorus, which determines the higher reactivity of the compound during thermal decomposition and its tendency to give oxygen to the polymer matrix at the charring stage.

Basic Attributes

• CAS No: 15099-32-8
• Chemical formula: AlO3P
• English name: Aluminum phosphite
• Molecular Weight: 105.953499
• Exact weight: 105.94
• PSA specifications: 69.2

Physico-chemical characteristics

The commercial product is a white to slightly yellowish crystalline powder; at a high degree of purification, the powder is pure white, odorless. The compound has good thermal stability: the temperature at which the technical product begins to decompose is about 360 °C, which is noticeably higher than the processing temperatures of most structural thermoplastics and allows the introduction of a fire retardant into the polymer melt without premature decomposition and loss of fire retardant properties. It is hygroscopic and slowly cakes in a humid atmosphere.

Scope of application

Aluminum phosphite is used as a phosphorus component of halogen-free fire retardant systems and as an auxiliary substance in plant protection.

• fire retardant and heat stabilizer in structural thermoplastics - polyamide (PA) and polybutylene terephthalate (PBT)
• synergist of phosphorus-nitrogen flame retardant compositions together with melamine and its derivatives in paint coatings, plastics and cable insulation
• auxiliary component of fungicidal preparations for plant protection
• corrosion inhibitor in certain metalworking processes

Mechanism of action

In fire-retardant compositions, aluminum phosphite works predominantly in the condensed phase. When the material is heated, the compound decomposes with the release of phosphorus-containing acids and phosphorus oxides, which catalyze the dehydration of the polymer chain and accelerate the formation of a carbonized layer on the surface of the material. A dense coke layer reduces the release of flammable volatile products into the flame zone and protects the underlying layers of polymer from heat flow, delaying the spread of combustion. Thanks to trivalent phosphorus, the compound exhibits a more pronounced reducing character compared to phosphate analogues and, due to this, more effectively synergizes with nitrogen-containing flame retardants, reducing the total dosage of additives required to achieve the required flammability class.

Storage and transportation

Store in a dry, well-ventilated warehouse, in tightly closed original containers, away from strong acids and oxidizing agents, upon contact with which toxic phosphine may be released. Protect the powder from moisture: hygroscopicity leads to caking and loss of flowability, which makes dosing difficult during compounding. When working with the product, use respiratory protection against dust, gloves and safety glasses, and avoid the formation of a dust cloud when pouring.