Flame retardancy polyurethane foam flammability

The low burning result and the self-extinguishing characteristic obtained were not surprising. I say this in hindsight, for the inherent flammability of polyurethane foam, in general, is almost entirely a function of the chemical composition of the solid polymer and one route used to produce flame retardant polyurethane foams has been to alter the structure of the ure-... 

Hilado conducted a comparative study on the flammability of great many flame-retarded polyurethane foam grades. The flammability of rigid polyurethane foams are markedly reduced by formation of an isocyanurate structure. The exploitation of this possibility is detailed in Section 5.1.5. 

Ironically, the reactor was used to produce Antiblaze 19, a flame retardant used in textiles and polyurethane foam. Antiblaze 19 is a cyclic phosphorate ester produced from a mixture of trimethyl phosphite, dimethyl methylphosphonate (DMMP), and trimethyl phosphate (TMOP). The final product is not considered flammable, but trimethyl phosphite is moisture sensitive and flammable, with a flash point of about 27 C. 

Zammarano, M. Gilman, J.W. Kramer, R.H. et al. Effect of nanoparticles on flammability of flexible polyurethane foams. Proceedings of 19th Annual BCC Conference on Flame Retardancy—Recent Advances in Flame Retardancy of Polymeric Materials, Stamford, CT, 2008. 

Bonsignore, P.V. Levendusky, T.L. Alumina trihydrate as a flame retardant and smoke suppressive filler in rigid high density polyurethane foams. J. Fire Flammability 1977, 8, 95-114. 

Flame Retardants. Among the isocyanate-based foams, polyurethane foams, both flexible and rigid, are flammable. Due to serious fire hazards of polyurethane foams, strict fire regulations have come out on the use of foams in the areas of furniture and public transportation. In addition, the use of rigid urethane foams in building insulation have resulted in stricter fire regulations. 

A large number of patents are concerned with the flame-retardance of polyurethane foams. Techniques for reducing the flammability characteristics of rigid polyurethane foams were commercialized quite early on most of their grades have been flame-retardant since the early sixties. However, effective flame-retardance of flexible polyurethane foams is still a problem, as the retarding agents may reduce the durability of the products. 

Isocyanate/Isocyanurate. Isocyanates react with polyols to form rigid polyurethane foams, a major type of thermoset plastics. While these are very useful in thermal insulation, they are limited by failure at high temperature and by flammability. One way to solve these problems is to convert part of the isocyanate to isocyanurate by cyclotrimeriza-tion (Fig. 3.64). Whereas the isocyanate-polyol reaction forms polyurethane rapidly at room temperature, the cyclotrimeiization of isocyanate to isocyanurate requires strong alkaline catalysis and heat to compete successfully. The resulting isocyanurate rings build considerable heat resistance (150 to 250°C, short-term <800°C) and flame-retardance into the polyurethane foam. They are useful for insulating pipelines and boilers. 

When rigid polyurethane and PIR foam construction panels are made using alkanes, they may require additional flame retardants to maintain the same fire performance characteristics. Chlorinated aliphatic hydrocarbons can have a beneficial effect on foam flammability and can also serve as minor components of blowing agent mixtures, provided that they are permitted... 

TEP is used as a flame retardant for making non-flammable polyurethane foams and polyurethane resins as well as a viscosity reducer for polyols and prr iolymers. 

Polymeric foamed materials are very specific in terms of ignitability and flame spread. It has been shown that differences in the surface area of foamed polymers and cell size have a larger effect on flammability than do density or differences in chemical structure. The chemical stmcture, of course, may dictate the surface area or porosity in the formation of foam. For example, flexible polyurethane foams can be ignited by a smoldering cigarette. A textile material normally used to enclose the foam, as is common in upholstered furniture and mattresses, actually helps ignition if snitable flame retardant-treated textiles are not used. 

Flammability. Rigid polyurethane foams, along with other organic plastics, have been the subject of much work in the field of flame retardance. A variety of phosphorus and/or halogen containing additives (reactive and non-reactive) are now available which improve the flame resistance of polyurethane foams. The choice of additives and of test methods is however best decided upon in the light of the application envisaged. Table 7 shows some typical properties. 

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