Flammability urethane foam

Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate.26 In vinyls (plasticized), arylphos-phates are frequently used with phthalate plasticizers. Their principal applications are in wire and cable insulation, connectors, automotive interiors, vinyl moisture barriers, plastic greenhouses, furniture upholstery, and vinyl forms. Triarylphosphates are also used, on a large scale, as flame-retardant hydraulic fluids, lubricants, and lubricant additives. Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. Blends of triarylphosphates and pentabromodiphenyl oxide are extensively used as flame-retardant additives for flexible urethane foams. It has been also... 

Burning may be considered another means of oxidation. Non-burning plastics are a must in commercial constructions according to building codes and are often required for automotive, electronic, and electrical applications. From the numerous thermoplastics, only the halogen-containing polymers, polyamides, polycarbonate, poly(phenylene oxide), polysulfone, and polyimides are self-extinguishing. Even these, such as poly (vinyl chloride), may become flammable when plasticized with a flammable plasticizer. Fire control can be the key to volume use of plastics. Polyester panels, urethane foam, and PVC tarpaulins account for nearly 90% of all fire retardants consumed. Consumption in 1967... 

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. 

The high flammability and toxic-gas generation of flexible and rigid urethane foams have been major problems in the urethane-foam industry, and accordingly considerable efforts have been focused on the production of substantially flame-retardant flexible foams. 

A number of flame retardants for rigid urethane foams have been developed over the past 30 years. Nevertheless, substantially flame-retardant, and fire-resistant rigid foams are not available, because the urethane linkage is thermally unstable and decomposes to produce low-molecular-weight flammable compounds. 

The addition of flame retardants, either additive or reactive types, can provide flame-retardant foams having low flame spread or surface flammability, but flame retardants do not improve the temperature resistance of these foams because the thermal stability or the dissociation temperature of the urethane linkage is relatively low and unchanged by the addition of flame retardants, i.e., the linkage dissociates at about 200°C to form the original components in polyol and polyisocyanate. The dissociation can result in further decomposition of polyol and polyisocyanate into low-molecular-weight compounds at elevated temperatures. For these reasons urethane foams are not temperature-resistant nor thermally stable. 

The above cited diol, when incorporated into a flexible polyurethane foam formulation at a 5.6% level (10 phr based on the polyol) produced a self-extinguishing urethane foam, based on the Motor Vehicles Safety Standard 302 Flammability Test. 

This forecast assumes that the furniture segment is fully penetrated by flexible urethane foam. Style changes may impact cushion dimensions somewhat, but are considered an insignificant factor in the forecast. Flammability issues remain unsettled however, this forecast assumes technology development will continue to keep urethane foam in the forefront as the best choice for cushioning applications. 

Finally, urethane foams will have a flammability performance permitting their general use in non-residential occupancies. These would include high risk mattress and later furniture uses. 

Poly(urethane) foams based on polyethers have now largely replaced polydiene rubbers in upholstery and flammability is a major disadvantage compared with traditional upholstery. A major problem is that it is not the fire itself that kills people but the toxic fumes that are produced in the smoke and this is exacerbated by certain types of flame retardant. There are no simple solutions to this problem. Foams in their very nature have a large surface area and a developing fire thrives on the accessibility of fuel from the exposed foam (Chapter 3). The most promising solution is to make the textile fabric surrounding the foam non-flammable so that the fire never reaches the foam itself. 

The Federal Aviation Authority in the USA commissioned NASA Ames Research Laboratory to examine the problems of aircraft interior flammability and they initially concentrated on limiting the effects of post crash fuel fire. The intense radiated heat ignites curtains, seats and decorative panels and it was reasoned that since the seats contained urethane foam, which will burn and generate asphyxiating gases, any improvement in upgrading the flammability resistance of the seats would provide a significant improvement in safety performance in the event of a post crash fire. 

Taking advantage of the many aromatic hydroxyl functions in conifer bark tannins, Hartmann (83) used ground bark as a polyol for reaction with isocyanates to prepare urethane foams with particularly good flammability resistance. Most uses for conifer bark tannins that involve reactions with the hydroxyl functions center on their complexation with cations. When sulfonated, condensed tannins can also be used as water-soluble heavy metal complexes. One of the more interesting of these applications is the development of water-soluble heavy-metal micronutrient complexes that have been used to correct iron deficiency in citrus... 

Methylene chloride is a widely used chemical solvent with a diverse number of applications. It was introduced as a replacement for more flammable solvents over 60 years ago. Methylene chloride is commonly used in paint removers and industrial adhesive formulations. It also is employed in the production of flexible urethane foams, pharmaceutical products, and plastics, as a cleaning agent for fabricated metal parts, and as an extraction solvent. 

Aryloxyphosphazene copolymers can also confer fireproof properties to flammable materials when blended. Dieck [591] have used the copolymers III, and IV containing small amounts of reactive unsaturated groups to prepare blends with compatible organic polymers crosslinkable by the same mechanism which crosslinks the polyphosphazene, e.g. ethylene-propylene and butadiene-acrylonitrile copolymers, poly(vinyl chloride), unsaturated urethane rubber. These blends were used to prepare foams exhibiting excellent fire retardance and producing low smoke levels or no smoke when heated in an open flame. Oxygen index values of 27-56 were obtained. 

---