Phosphorus-based fire retardants

The addition of phosphorous-based plasticizers will provide a degree of fire retardancy to the polyurethane. Fryol PCF and CEF have been used in polyurethane systems. Most phosphorus-based fire retardants are thin liquids that are compatible with polyurethanes. Because of the very varied nature of fire-resistant tests, the material made must be tested to the appropriate standard. 

Chigwada, G., Jash, P., Jiang D.D., and Wilkie, C.A. 2005. Fire retardancy of vinyl ester nanocomposites Synergy with phosphorus-based fire retardants. Polym. Deg. Stab. 89 85-100. 

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. 

The possible synergy between nanofillers and phosphorus-based fire retardants such as tricesylphosphate (TCP) and resorcinol diphosphate (RDP), has been investigated. " RDP, for example, gave a reduction in PHRR between 47 and 61% at a loading of 30 wt%. No improvement was obtained by combining an organoclay (Cloisite 15A) with RDP (30 wt%) the reduction in the PHRR was between 48 and 55%. 

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. ... 

Levchik, S. V. and Weil, E. D., A review of recent progress in phosphorus-based flame retardants, J. Fire... 

Levchik, S.V., Camino, G., Costa, L., and Levchik, G.F. 1995. Mechanism of action of phosphorus-based flame retardants in nylon 6.1. Ammonium polyphosphate. Fire Mater. 19 1-10. 

Use Phosphorus-based catalyst in organic and latex-based fire-retardant intumescent paints, mastics, and polymers. 

Phosphorus-based flame retardants include tris(l,3-dichloroisopropyl) phosphate, used in polyurethane foams and polyester resins. Once again, there is debate concerning toxic side-effects of such products although these flame retardants may save lives, they produce noxious fumes during a fire. 

Though closed-cell rigid polyurethane foams are excellent thermal insulators, they suffer form the drawback of unsatisfactory fire resistance even in the presence of phosphorus- and halogen-based fire retardants. In this context, polyisocyanurates, which are also based on isocyanates, have shown considerable promise. Isocyanurate has greater flame resistance then urethane. Although rigid polyurethane is specified for the temperatures up to 200°F (93°C), rigid polyisocyanurate foams, often called trimer foams, withstand use temperatures to 300°F (149°C). Physical properties and insulation efficiency are similar for both types. 

With the exception of alumina hydroxides, fire-retardant phosphorus compounds are now used in greater quantities than any of the other main types of retardants, that is, antimony oxide, borates or halogenated hydrocarbons. Advantages claimed for organophosphorus-based fire retardants are relatively low toxicity and minimum harmful volatiles under burning conditions [37]. 

Several approaches have been used to make polymers fire-retardant. Phosphorus-based flame retardants have been effectively used in a wide variety of polymeric materials. The efficiency of phosphorus compounds is often dramatically increased in the presence of certain nitrogen compounds. Thus, the improved flame resistance of polyesters in the presence of triphenylphosphine oxide and Nylon-6 has been attributed to the synergistic effect of phosphorus and nitrogen atoms. However, the fire-retardant additives (1) frequently influence the decomposition reaction in... 

Solid (Condensed) Phase Sohd phase fire retardant(s) alter the physical burning characteristics by either forming an insulative fire barrier or by changing the surface morphology to interfere with the release or generation of combustible gases. This mechanism is commonly seen with phosphorus-based flame retardants. 

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. 

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