Aluminium diethyl phosphinate is a chemical compound with formula Al()₃. It decomposes above 300 °C.

Applications

In the family of dialkyl phosphinic acid salts, aluminium diethyl phosphinate has been found to be an excellent

flame retardant The term flame retardants subsumes a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an ignition source and ...

for use in engineering plastics such as

polyamide A polyamide is a polymer with repeating units linked by amide bonds. Polyamides occur both naturally and artificially. Examples of naturally occurring polyamides are proteins, such as wool and silk. Artificially made polyamides can be made through ...

s, polyesters, thermosets and elastomers. It was developed by

Hoechst Hoechst, Hochst, or Höchst may refer to: * Hoechst AG, a former German life-sciences company * Hoechst stain, one of a family of fluorescent DNA-binding compounds * Höchst (Frankfurt am Main), a city district of Frankfurt am Main, Germany ** Fra ...

, later by Clariant chemicals and Ticona. In 2004 and 2012, Clariant chemicals opened its first and second commercial production lines respectively in Huerth-Knapsack near Cologne. Aluminium diethyl phosphinate acts as a flame retardant in the condensed phase in contributing to charring of the polymer matrix and thus protecting the substrate against heat and oxygen attack. In parallel it acts in the gas phase by radical reactions removing from the combustion zone the high energy radicals H. and OH., which determine flame propagation and heat release. The phosphinate partly vaporises and partly decomposes to volatile diethyl phosphinic acid and an aluminium phosphate residue, which acts as a barrier for fuel and heat transport. Aluminium diethyl phosphinate is used as a halogen-free flame retardant for

s, polyesters,

thermoset In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening (" curing") a soft solid or viscous liquid prepolymer ( resin). Curing is induced by heat or suitable radiation ...

resins (e.g. epoxies) in electrical engineering and electronics (E&E) applications for switches, plugs, PC fans, and structural and housing components. Smartphones, washing machines, and airplane parts, among others, contain the product. Other applications include thermosetting resins and adhesives as well as cable sheaths and insulation made from thermoplastic elastomers. Aluminium diethyl phosphinate can give these plastics flame retardant properties that are otherwise only achievable with expensive high-performance plastics, which are less easy to work with. Aluminium diethyl phosphinate is often used in combination with other halogen-free flame retardant additives like melamine polyphosphate or melamine cyanurate. In glass fibre reinforced (GF) polyamide 6 (

Nylon 6 Nylon 6 or polycaprolactam is a polymer, in particular semicrystalline polyamide. Unlike most other nylons, nylon 6 is not a condensation polymer, but instead is formed by ring-opening polymerization; this makes it a special case in the compar ...

) and 66 (

Nylon 66 Nylon 66 (loosely written nylon 6-6, nylon 6/6, nylon 6,6, or nylon 6:6) is a type of polyamide or nylon. It, and nylon 6, are the two most common for textile and plastic industries. Nylon 66 is made of two monomers each containing 6 carbon atoms, ...

) formulations as well as in polyesters like

polybutylene terephthalate Polybutylene terephthalate (PBT) is a thermoplastic engineering polymer that is used as an insulator in the electrical and electronics industries. It is a thermoplastic (semi-)crystalline polymer, and a type of polyester. PBT resists solvents, ...

(PBT) and PET, aluminium diethyl phosphinate shows excellent performance in the UL 94 flammability tests (

UL 94 UL 94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing, is a plastics flammability standard released by Underwriters Laboratories of the United States. The standard determines the material� ...

V0 specification is met down to 0.4 mm), as well as in the glow wire tests required for appliances. Here, formulations with aluminium diethyl phosphinate meet the glow wire ignition test (GWIT) at 775 °C and the glow wire flammability test (GWFI) at 960 °C. Another important criterion in E&E applications is the

Comparative Tracking Index The Comparative Tracking Index (CTI) is used to measure the electrical breakdown (tracking) properties of an insulating material. Tracking is an electrical breakdown on the ''surface'' of an insulating material wherein an initial exposure to elec ...

(CTI), which determines the risk of electrical tracking of insulating material that is exposed to contaminating environments and surface conditions. With formulations containing aluminium diethyl phosphinate, the highest requirement of 600 V (numeric value of the highest voltage at which an electrical insulating material withstands 50 drops of electrolytic test solution) is achieved. Further benefits of polyamides and polyesters containing aluminium diethyl phosphinate are low smoke density which makes them suitable for rolling stock applications to EN 45545, as well as good light stability which is needed for outdoor applications. The EU’s

RoHS The Restriction of Hazardous Substances Directive 2002/95/EC (RoHS 1), short for Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, was adopted in February 2003 by the European Unio ...

directive forced E&E manufacturers to switch to

lead-free solder Solder (; NA: ) is a fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces after cooling. Metals or alloys suitable ...

systems running at about 30 °C higher temperatures than traditional systems. In particular, in the so-called surface mount technology (SMT) used to connect semiconductor components mechanically and electrically to circuit boards, the resins have to withstand peak temperatures of 260 °C and more during the soldering process. This triggered the rapid growth of polymer resins based on polyamides with melting points above 300 °C, in particular PPAs and

Nylon 46 Nylon 46 (nylon 4-6, nylon 4/6 or nylon 4,6, PA46, Polyamide 46) is a high heat resistant polyamide or nylon. DSM is the only commercial supplier of this resin, which markets under the trade name Stanyl. Nylon 46 is an aliphatic polyamide formed by ...

. The application requires the resin to pass GWIT and UL94 ratings mentioned above. Aluminium diethylphosphinate confers this flame retardancy on polyamides whilst meeting the other requirements such as CTI. A large variety of synergists is used to tune properties of polyamide and polyester compounds.

Human health and the environment

Human health and environmental facts of aluminium diethyl phosphinate are summarized in a fact sheet. Further data are given in the Arcadis Study carried out on behalf of the European Commission Health & Consumers DG, Contract number 17.020200/09/549040: “Identification and evaluation of data on flame retardants in consumer products. Final Report” of 26 April 2011, Chapter 5.23, p. 168. Aluminium diethyl phosphinate has also been investigated in projects of the US EPA Design for Environment (DfE) programme and in the European FP7 research project Enfiro.''Enfiro: Life cycle assessment of environment-compatible flame retardants'' (Sep 2009 to Nov 2012) http://cordis.europa.eu/projects/226563 With the exception of being persistent and thus not readily biodegradable, aluminium diethyl phosphinate has been shown to have a favourable environmental and health profile.

References

{{reflist, 30em Phosphinates Aluminium compounds Flame retardants