Phosphorus-based polyurethanes

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. 

Shao, C. H., Huang, J. J., Chen, G. N., Yeh, J. T., and Chen, K. N., Thermal and combustion behaviors of aqueous-based polyurethane system with phosphorus and nitrogen containing curing agent, Polym. Degrad. Stab., 1999, 65, 359-371. 

Wang, T. Z. and Chen, K. N., Introduction of covalently bonded phosphorus into aqueous-based polyurethane system via postcuring reaction, J. Appl. Polym. Sci., 1999, 74, 2499-2509. 

FR-D. [FMC] Phosphorus-based diol reactive flame retar t for rigid polyurethane foam. 

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. 

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 ideal approach to reducing volatile yield is to use an inherently stable matrix polymer and reference has already been made to the chemical structures that confer maximum thermal stability. Alternatively, there are additives which function in the condensed phase and modify the degradation pathway. Phosphorus-based additives, usually working through a phosphoric acid intermediate, are popular additives, particularly for polyurethanes. They act predominantly in the condensed phase, increasing char yield and reducing volatile production. 

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. 

Akzo Nobel sells a phosphorus-based FR called Fyrol PNX, containing 19% phosphorus as a replacement for deca-BDE in furniture and automotive foam made of flexible polyurethane. 

Albemarle s combined net sales rose from US 941 M in 2000 to US 1110 M in 2003, despite very difficult trading conditions. Net income fell in the same period from US 102 M to US 72 M, and long-term debt rose from US 97 M to US 228 M These figures are partly explained by the fact that several acquisitions have been made. They included Akzo Nobel s refinery catalysts, the Korean distributor Taerim, Arkema s fine chemicals bromine business, Rhodia s phosphorus based flame retardants business for polyurethanes, the fuel and lubricant antioxidants business of Ethyl, the fine chemicals business of ChemEirst, and Martinswerk. 

Flame retardant additives can also modify the types of products that are released during incineration of waste polymers and in this way the flame retardants are contaminants which also affect the quaternary recycling of polymers (that is, the incineration of polymers to recover heat). For example, the thermal degradation of polyurethane, PU, can produce a complex mixture of products. However, in the presence of a common phosphorus-based flame retardant (such as ammonium polyphosphate), aniline (which is quite toxic) becomes a relevant volatile combustion product. ... 

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. 

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. 

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. 

Polycondensation of Compounds Containing a Phosphate Linkage. Polycondensation of tris(2-chloroethyl) phosphate, preferably in the presence of a nucleophilic catalyst, affords an oligomeric phosphate which was for a time produced by this process as a flame retardant for polyurethane foams, thermoset resins, and air-fllter products (140-142). A preferred method, avoiding a chlorinated coproduct, is based on addition of phosphorus pentoxide and ethylene oxide to the tris(2-chloroethyl) phosphate, as discussed above. 

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