Flame retardant compounds containing phosphorus

A phosphorus-nitrogen S5mergism is seen in the flame retardant action. Therefore, flame retardant compounds containing phosphorus-nitrogen bonds have been developed. Examples are shown in Table 7.5. 

A 2/1 blend of polycarbonate and polyethylene terephthalate (PC/PET) was flame retarded with bromine, phosphorus, a blend of bromine and phosphorus, and compounds containing both phosphorus and bromine in the same molecule. All compositions contained 0.5 % Teflon 6C as a drip inhibitor and where specified 5 % of an impact modifier. 

Fire Retardants for Ceftnlosics. Phosphorus-containing materials are by far the most important class of compounds used to imparl durable flame resistance lo cellulose. Flume-retardant finishes containing phosphorus compounds usually also contain nitrogen or bromine or sometimes huth. 

The fire resistance of polyurethanes is based on the introduction of flame retardant compounds including polyols, containing chlorine, bromine or phosphorus in their structure. The polyols containing chlorine, bromine or phosphorus are linked chemically in the polyurethane structure and lead to self-extinguishing polyurethanes, with a permanent flame retardancy. 

Fire-retardant treatment Hammability of acrylic textiles can be reduced by using (meth)acrylates containing phosphorus monomers known to be effective as flame-retardant compounds (Price et al., 2002). Tsafack et al. (2004) smdied the plasma-grafted thin layer of phosphorus polymer by plasma-induced graft-polymerization. The formation of a characteristic protective char layer during the burning test was observed for the treated compounds whereas the untreated ones burned without residuals (Tsafack et al., 2004). 

The generally accepted explanation of the flame-retarding action of phosphorus-containing substances is that the very stable poly(meta-phosphoric acid) formed during the thermal decomposition of the plastic material creates an insulating and protecting surface layer between the polymer and the flame [27]. It has been found that the flame retardancy effect of these compounds depends not only on their concentration but on the heat of their decomposition reaction, which depends on their chemical structure. Compounds containing phosphorus in the lowest oxidation state are the most efficient. The structural effect is responsible for the fact that bromoalkyl phosphate with a bromine atom bound to a secondary carbon of an alkyl substituent shows a better flame retardancy. 

Table 12.3. Flame retardancy of brominated phosphorus-containing compounds...

When the efficiency of different flame retardants is compared, phosphorus compounds are better than those containing antimony, chlorine, and bromine. The most efficient are the synergetic mixtures of phosphorus and bromine-containing compounds the bromine content can be decreased by adding an antimony compound, as shown in Table 12.6 [40]. 

In recent years, many poly(phosphazenes), [RoPN]n, with a variety of substituents at phosphorus have been prepared and they often exhibit useful properties including low temperature flexibility, resistance to chemical attack, flame retardancy, stability to UV radiation, and reasonably high thermal stability. (1,2) Compounds containing biologically, catalytically, or electrically active side groups are also being investigated. (3,4)... 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

Commercially available flame retardants include chlorine- and bromine-containing compounds, phosphate esters, and chloroalkyl phosphates. Recent entry into the market place is a blend of an aromatic bromine compound and a phosphate ester (DE-60F Special) for use in flexible polyurethane foam (8). This paper describes the use of a brominated aromatic phosphate ester, where the bromine and phosphorus are in the same molecule, in high temperature thermoplastic applications. 

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

Flame Retardants. Bromine compounds make up an important segment of the market for flame retardants used in polymers. Additive flame retardants are added to polymers during processing reactive flame retardants react chemically to become part of the polymer chain itself In addition to the compounds listed in Table 3, a number of proprietary mixtures and phosphorus—bromine-containing flame retardants are also sold (see Flame retardants, HALOGENATED, FLAME RETARDANTS). 

D. Price, K. Pyrah, T.R. Huh, G.J. Milnes, J.R. Ebdon, BJ. Hunt, P. Joseph, and C.S. Konkel, Flame retarding poly(methyl methacrylate) with phosphorus-containing compounds Comparison of an additive with a reactive approach. Polym. Degrad. Stab., 74,441 447 (2001). 

K.J. Bullett (formerly Pyrrah), Flame retarding acryhc and styrenic polymers by modihcation with phosphorus-containing compounds, PhD thesis, University of Salford, 2002. 

The red allotropic form of phosphorus is relatively nontoxic and, unlike white phosphorus, is not spontaneously flammable. Red phosphorus is, however, easily ignited. It is a polymeric form of phosphorus, thermally stable up to ca. 450°C. In its finally divided form, it has proved to be a powerful flame-retardant additive.18 Elemental red phosphorus is a highly efficient flame retardant, especially for oxygen-containing polymers such as polycarbonates and polyethylene terephthalate). Red phosphorus is particularly useful in glass-filled polyamide 6,6, where high processing temperature (about 280°C) excludes the use of most phosphorus compounds.19 In addition, coated red phosphorus is used to flame retard nylon electrical parts, mainly in Europe and Asia.20... 

Ammonium polyphosphates, on the other hand, are relatively water insoluble, nonmelting solids with very high phosphorus contents (up to about 30%). There are several crystalline forms and the commercial products differ in molecular weights, particle sizes, solubilities, and so on. They are also widely used as components of intumescent paints and mastics where they function as the acid catalyst (i.e., by producing phosphoric acid upon decomposition). They are used in paints with pentaerythritol (or with a derivative of pentaerythritol) as the carbonific component and melamine as the spumific compound.22 In addition, the intumescent formulations typically contain resinous binders, pigments, and other fillers. These systems are highly efficient in flame-retarding hydroxy-lated polymers. 

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