Phosphorus-based polyamides

Inorganic phosphorus compounds are also used as flame-retardants. Elemental red phosphorus itself is applied, for example, in polyurethane foams and more recently in polyamides. Some marketed types of red phosphorus-based flame-retardants are collected in Table 5.6. 

Most phosphorus based FRs tend to promote char formation, which gives several desirable benefits. The char is difficult to ignite, it acts as a barrier between polymer and flame, it restricts oxygen access, and it reduces the rate of heat generation. This works well for polyesters, PU and polyamides, but when it comes to st3Tenic polymers or polyolefins, there is often a need to combine phosphorus systems with other additives. 

A HALS-based additive system has been developed by Clariant based on salt-like reaction products of HALS with phosphorus-containing organic acids [199] or carboxylic acids [200]. Despite their salt-like character, these additives are said to stabilise in the normal HALS manner, and additionally provide improved processing, mechanical properties and appearance. They are specifically aimed at polyesters and polyamides. An example of one of these compounds is the... 

Clariant has introduced new products based on their phosphonic acid metal salt technology that has been under development for some time. This technology is aimed at engineering resins, the first of which has been polyamides, and can be added at aroimd 15% loading. This makes it more cost effective than red phosphorus and even some brominated FRs used for the same applications. 

Another class of reactive chemical with effective fire-retardant properties is based on phosphorous derivatives (phosphorus, phosphates, etc ). It is mainly used with oxygen or nitrogen-rich polymers like polyesters and polyamides, as it promotes the formation of char during the decomposition of these matrices (Horrocks and Price, 2001 Mouritz, 2007 Laoutid et ah, 2009). 

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