Phosphorus-Containing Fire Retardants

There is an evolving concern about the use of some particular organophosphates such as tricresyl phosphate, tri-n-butyl phosphate, and triphenyl phosphate [94,108-110]. Animal studies have shown that these phosphate esters can cause allergies, learning problems, and deterioration in sperm production and can influence the white and red blood cell counts of humans [109]. In a recent publication [110], levels of flame retardants in indoor air at electronics scrap recycling plant and other work environments were considered 15 brominated FRs and 9 organophosphorus compounds were analyzed. Although the measured concentrations found in all 

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Phosphorus-containing fire retardants can be active in the condensed phase or in the vapor phase, or in both phases.88 The relative predominance of the different mechanisms actually operating in a... 

There are also a number of other hydroxides and hydroxycarbonates, which are increasingly being used as alternatives to halogen- and phosphorus-containing fire-retardant additives, since they are perceived to have less adverse impact on the environment. 

Polyolefin Foams. Antimony oxide/chlorowax combinations or other aliphatic chlorine sources are generally used to fire retard polyolefin foams. Because of the higher processing temperatures required (up to 280 C or 536°F), when using azo blowing agents, the antimony ox-ide/chlorine system is inadequate, and in these cases phosphorus-containing fire-retardant systems are preferred (38). 

The author thanks Schneller LLC for permission to pubUsh this chapter. The following colleagues are acknowledged Dr Edward Wed, Polytechnic, NYU, NYC, for information on smoke suppression and flame retardants in PVC and Dr John Mara of Songwon International for information on phosphorus-containing fire retardants. 

Levchik, G. F. Murashko, E. A. (2001). Phosphorus-Containing Fire Retardants in Aliphatic Nylons, Fire and Polymers, Chapter 17, pp 214. 

Wolf, R. (1986) Phosphorus-containing fire retardants for transparent plastics and film. Kunstoffe, 76(10), 943-947. 

Whilst rigid closed-cell polyurethanes are excellent thermal insulators they do suffer from a limited and often unsatisfactory level of fire resistance, even in the presence of phosphorus-containing and halogen-containing fire retardants. Considerable promise is now being shown by the polyisocyanurates, which are also based on isocyanate chemistry. 

Green, J., Phosphorus-containing flame retardants, in Fire Retardancy of Polymeric Materials, Grand, A. F. and Wilkie, C. A. (Eds.), 2000, Marcel Dekker, New York, pp. 147-170. 

Horrocks, A.R., Davies, P., Alderson, A., and Kandola, B.K. 2007. The potential for volatile phosphorus-containing flame retardants in textile back-coatings. J. Fire Sci., 25(6) 523-540. 

Green, J. (199,3), A review of phosphorus-containing flame retardants. Fire Sci. 10,470-487. 

Fires involving materials treated with anti-ChEs or bulk pesticides stores (CM and OP) may release both the unaltered anti-ChE and thermal decomposition products. Also, certain phosphorus-based fire retardants that arc subjected to heat and flame in a fire may result in the generation of anti-ChEs and other toxic materials. Thus, although fire retardants may slow the rate of fire progression, their involvement in a conflagration may result in an increase in the toxic potency of combustion products (Purser, 1992). For example, polyurethane foams treated with a trimethylol propane polyol base containing phosphoms-based retardants formed a highly neurotoxic combustion product [irimethylolpropane phosphate (TMPP) Petajan et at., 19751. 

Epoxy Resins, in the combustion of epoxy resins, phosphorus inhibits the evolution of fuel gases and increases char (176). Much attention has been given to phosphorus additives or reactives in epoxy resins used as coatings for the purpose of increased adhesion to surfaces (177,178) and for fire resistance. More recently, a great deal of attention has been given to phosphorus-containing, flame-retarded electrical/electronic laminates and encapsulated electronic parts. 

Gonoshilov, D. G., Keibal, N. A., Bondarenko, S. N., Kablov, V. F. (2010). Phosphorus Boron Containing Fire Retardant Compounds for Polyamide Fibers Proceedings of the 16th International Scientific and Practical Conference Rubber industry Raw materials. Manufactured materials. Technologies, Moscow, 160-162. 

These commercial examples provide evidence that inclusion of nanoparticle species can indeed reduce the overall flame retardant additive levels required to achieve a desired fire performance level. To corroborate this, work in our laboratories ° with PA6 and PA6,6 films and selected phosphorus-containing flame retardants suggests this to be the case when selected functionalized nanoclays are also present, and this work is reviewed below. 

The first fire retardant polyester containing a reactive fire retardant monomer was introduced by the Hooker Electrochemical Corporation in the early 1950 s containing chlorendic acid as the reactive monomer (6). This pioneering development rapidly led to the introduction of variety of reactive halogen and phosphorus containing monomers, such as tetrabromophthalic anhydride, chlorostyrene and tetrabromobisphenol A, which found application in a wide variety of condensation polymer systems. 

In 2000, NEC developed an epoxy resin with what it describes as a fire-retardant structure that avoids the need for either TBBA or phosphorus-based flame retardants in circuit boards. The new resin contains a metal hydroxide retardant. The company claims the new board is almost totally free of pollutants, and is easy to process and thermally recycle. By also integrating flame retardant properties within the board, use of the metal hydroxide is minimised, while offering good electrical properties, higher heat resistance and improved processing characteristics. ... 

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 paper-impregnation drying oven exhausts contain high concentrations (10—20% LEL) of alcohols and some resin monomer. Vinyl resins and melamine resins, which sometimes also contain organic phosphate fire retardants, may be used for air filters. The oiganic phosphates could shorten catalyst life depending on the mechanism of reduction of catalyst activity. Mild acid leaching removes iron and phosphorus from partially deactivated catalyst and has restored activity in at least one known case. 

Ebdon, J. R., Hunt, B. J., Joseph, P, and Wilkie, T. K., Flame retardance of polyacrylonitriles covalently modified with phosphorus and nitrogen-containing groups, in Fire Retardancy of Polymers New Strategies and Mechanisms, Hull, T. R. and Kandola, B. K. (Eds.), 2009, Royal Society of Chemistry, Cambridge, U.K., pp. 331-340. 

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