Polyurethane foam insulation is a superior insulator with high RValue. However, as noted by Paabo and Levin (1987), many studies into the decomposition of polyurethane foams do not differentiate between flaming and non-flaming decomposition, and focus on the temperature of decomposition rather than the presence of flames. However, unlike a real fire, the heat flux remains constant, and so when the oxygen concentration falls, the flame may be extinguished. polyurethane foam production and up to a point the amount of water added will be inversely proportional to the density of the foam. Science 187:p742744, Wisnewski AV, Lemus R, Karol MH, Redlich CA (1999) Isocyanate-conjugated human lung epithelial cell proteins: A link between exposure and asthma? The results indicated that the formation of the precursor, TDI, was much faster and preferable to depolymerisation when the volatile compounds could escape. The incapacitating Ct product corresponds to CO at a dose of 35 000LL1min (approximately equal to ppm min), predicting incapacitation at around 1200ppm for 30min exposure, and an exponential relationship for HCN (because asphyxiation by HCN exposure does not fit a linear relationship), predicting incapacitation at around 82ppm for 30min exposure. Diesel engines use the principle of _____ to ignite fuel vapor. Recent work by Allan et al. 1 The conditions specified are: 25kWm2 without piloted ignition; 25kWm2 with piloted ignition; 50kWm2 without piloted ignition; and 50kWm2 with piloted ignition. Furniture, upholstery and curtains However, while the char produced when the polymer was heated at 370C contained only 20% of the total nitrogen from the polymer, 40% of that (8% of the total nitrogen in the polymer) was recovered as HCN when the char was burned at 600C. The authors tested a rigid polyurethane foam using a NBS cup furnace (as described in Levin et al. VOCs have the ability to vaporize, or off-gas, at room temperature. The detection of the amino MDI derivative in the tar further supports the literature reports of a secondary decomposition mechanism where isocyanates trapped in the condensed phase are converted irreversibly into their amine derivatives. TDI is primarily used in the production of flexible foams, which are used in the furniture and interior industries. Under well-ventilated flaming (<0.8), the yields of CO2 and NO2 were at their highest, while the yields of CO and HCN were at their lowest. I recently purchased a memory foam (polyurethane) mattress and was looking online to see how long they take to "air out". Levin BC, Fowell AJ, Birky MM, Paabo M, Stolte A, Malek D (1982) Further development of a test method for the assessment of the acute inhalation toxicity of combustion products. Woolley et al. These polyols will fragment and volatilise as the temperature increases, leaving behind a char (>600C). This equation only relates to lethality, or cause of death. Polyurethane foams based on polyether polyols will have a lower decomposition temperature in air than polyester polyol based foams. The test room was 2.43.03.0m with a door (dimensions not specified) and a 1 to 2kg slab of foam in the centre of the room. A more recent assessment by Marsh and Gann (2013) tested a flexible polyurethane foam with a cotton polyester cover in a range of test methods including the radiant heat apparatus (NFPA 269 2012), the ISO 56592 (2012) smoke density chamber, a controlled atmosphere cone calorimeter (ASTM E 1354) and the steady state tube furnace (ISO/TS 19700 2013). Michal (1982) reported a similar trend at a fixed air flow rate. Thermal decomposition of polyurethanes is usually the reverse of polymerisation, resulting in the formation their precursor functional compoundsdiisocyanates, diamines and dihydroxy compounds. Some methods have proved incapable of properlyreplicating the most toxic under-ventilated fire condition, where the yields of carbon monoxide and hydrogen cyanide are greatest, while other methods have shown good correlation with large scale test data. A comprehensive review of fire retardants and their use in polyurethane foams was published by Singh and Jain (2009). Is Memory Foam Toxic? | Sleep Foundation Non-fatal UK fire injuries requiring hospital treatment, 1955-2013 (UK Fire Statistics 2013). This will result in a HCN yield related that specific furnace temperature. That smell comes from volatile organic compounds, or VOCs, chemicals used in the mattress manufacturing process. In particular, the ventilation condition has a . This shows that the reactions of isocyanates are much faster with amines and slower with carboxylic acids, urethanes and amides than for the alcohols used in polyurethane production. In a letter to the editor of the journal, Barbrauskas et al. Isocyanurate rings are the most thermally stable in an inert atmosphere and decompose between 270 and 300C. Google Scholar, Schartel B, Hull TR (2007) Development of fire-retarded materials - interpretation of cone calorimeter data. The standard specifies four test conditions, but fails to link them to particular fire scenarios. NBSIR 832719. (2011) developed a mechanism based on both condensed and gas-phase decomposition in air. In contrast to the relativelywell-defined effects of asphyxiants, the effects of exposure to irritants are more complex. It gives off toxic gasses and smoke, which makes it difficult to evacuate and put out a fire. This is due to the concentration of oxygen directly under a flame being close or equal to 0% (Schartel & Hull 2007). In an attempt to improve the understanding of the thermal decomposition of polyurethanes, Rogaume et al. However, no amines were detected in the vapour phase. 1999). As the global usage of polyurethane foams is expected to continue to increase yearly, it is important that the fire community have a clear understanding of the fire toxicity of polyurethane foams and the reasons why they produce significant amounts of toxic gases during combustion. CO and HCN are the main asphyxiants produced during the combustion of polyurethanes and there have been a large number of studies published regarding their yields. The trimerisation results in a highly stable isocyanurate ring which confer additional thermalstability to polyisocyanurates (Scheme7). The authors acknowledged that the lower nitrogen recovery fraction for the flexible foam could be due to fuel nitrogen being lost as isocyanates, which are known to escape into the effluent plume, while for rigid foams they are more likely to be trapped in the burning solid (Woolley & Fardell 1977). (2014) on the catalytic decomposition of rigid polyurethane foam waste showed that ammonia, hydrogen cyanide and both nitrogen oxide and nitrogen dioxide were produced at temperatures up to 1100C. The toxic hazards associated with fire and the inability of victims to escape from fire atmospheres may be considered in terms of major hazard factors: heat, smoke and toxic combustion products (Hartzell 1993). The open cone calorimeter replicates the early well-ventilated stage of flaming where a fire would be too small to produce enough toxicants to cause harm except in very small enclosures. While well-ventilated fire scenarios are routinely used for assessment of flammability, because the object is to stop the fire growing to the out of control stage, where fire toxicity is concerned, the important fire stages are under-ventilated. The resulting substituted urea can then react with another isocyanate to produce a biuret linkage (Scheme4). Fire and Materials 19:p6164, Shufen L, Zhi J, Kaijun Y, Shuqin Y, Chow WK (2006) Studies on the Thermal Behavior of Polyurethanes. ISO 13571 (2007) considers the four major hazards from fire which may prevent escape (toxic gases, irritant gases, heat and smoke obscuration). At lower temperatures, decomposition differs, depending on the composition and physical properties of the polymer, although clear trends can be identified. Investigations by Hertzberg et al. TNO Prins Maurits Laboratory, The Netherlands. For a fixed chamber volume (0.51m3), assuming complete combustion, the sample thickness will dictate the ventilation condition, thus a thin sample will burn under well-ventilated conditions with minimum toxic products, while a thicker sample might be expected to produce a high yield of CO and other products of incomplete combustion. (1986) investigated the toxicity of flexible polyurethane foam and a polyester fabric both separately and together. Toxic product yields frommaterials involved in fires depend on a number of factors. However, this did not take into consideration the incapacitating effects of the release of irritant gases. At higher temperatures the decomposition of the foams produced increasing amounts of HCN from 600 to 900C, followed by a sharp rise between 9001000C. The peak HCN value reached was 10mg per g1 in the under-ventilated tests. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme 5). The Purser model, presented in equation1, uses \( {\mathrm{V}}_{{\mathrm{CO}}_2} \) a multiplication factor for CO2 driven by hyperventilation, therefore increasing the FED contribution from all the toxic species, and incorporates an acidosis factor A to account for toxicity of CO2 in its own right (ISO 13344 1996). 1981), probably because of increased use of nitrogen-containing synthetic polymers. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. The authors noted that in both the flaming and non-flaming combustion of the polyurethane foam, the concentrations of toxicants did not reach high enough concentrations to predict deaths. Taking this into consideration, the reported yields of isocyanates, aminoisocyanates and amines are still relevant, as the results of Blomqvist et al. Most fuel nitrogen is released as N2, but in well-ventilated combustion conditions a proportion is released as oxides of nitrogen (mainly NO) and in under-ventilated combustion conditions a proportion is released as HCN (Purser & Purser 2008a). Toxicology 115:7, Henneken H, Vogel M, Karst U (2007) Determination of airborne isocyanates. Will polyurethane melt under heat? - remodelormove.com The authors studied decomposition at 900C of foams, partly decomposed foams, smokes, and pure MDI to assess the hydrogen cyanide (HCN) content and noted that the yields of HCN were directly related to the nitrogen content. In the gas phase, isocyanates, amines and yellow smoke will begin to decompose at >600C into low molecular weight nitrogen containing fragments (such as benzonitrile, aniline and hydrogen cyanide (HCN)). During polymerisation, isocyanates undergo a number of distinct reactions. The strain of two electronegative atoms (N and O) results in electron density being pulled away from the carbon atom, giving it a strong partial positive charge. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. This is unusual as this test method is usually well-ventilated and the results are not similar to reports of other authors (such as Levin et al. ISO 56592 (2012) Plastics - Smoke generation - Part 2: Determination of optical density by a single-chamber test, ISO 56601 (2002) Fire tests Reaction to fire Part 1: Rate of heat release from building products (cone calorimeter method), ISO 9705 (1993) Fire tests Full-scale room tests for surface products, Kaplan HL (1987b) Effects of irritant gases on avoidance/escape performance and respiratory response of the baboon. Polymer International 53:p15851610. Polymer Degradation and Stability 98:535541, Anderson RA, Watson AA, Harland WA (1981) Fire Deaths in the Glasgow Area: I General Considerations and Pathology. These types of approaches have used existing rat lethality data, as described in ISO 13344 (1996) or more recently, based on the best available estimates of human toxicity thresholds as described in ISO 13571 (2007). (1991a) compared a number of test methods. 5-step decomposition mechanism for flexible polyurethane foam (Rogaume et al. Journal of Fire Sciences 8:p6379, BS 6853 (1999) Code of practise for fire precautions in the design and construction of passenger carrying trains. Since 2004, by law, the U.S. requires all mattresses to be fireproof to a specific temperature point and ever since the toxicity levels in foam memory mattresses have increased. 2 In particular, reports that used non-standard tube furnace apparatus lacked sufficient information about the conditions of the experiment and as such were not included. However, many people fail to escape from fires because of the incapacitating effect of smoke (obscuring visibility) and its irritant components which cause pain, preventing breathing and escape or reason death occurred. Cite this article. This suggests that the nitrogen in the char will more readily form HCN, even when the flaming is well-ventilated. 23. The review refers to a publication by Babrauskas et al. Equation Early work by Woolley et al (1975) indicated that the decomposition of polyurethanes up to around 600C resulted in the volatilisation of fragmented polyurethane and subsequent release into a nitrogen rich yellow smoke, containing partially polymerised isocyanates and droplets of isocyanate from the foam. Fire and Materials 25:p7181, Blomqvist P, Hertzberg T, Tuovinen H, Arrhenius K, Rosell L (2007) Detailed determination of smoke gas contents using a small-scale controlled equivalence ratio tube furnace method. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. As the main reactive group that isocyanates react with, polyols are a major component of the resulting polyurethane product. Common polyurethane functional groups i) urethane ii) urea iii) carbodiimide iv) uretdione v) isocyanurate. This makes foam mattresses very harmful. There are two reasons for this: The yields of the major toxic products (carbon monoxide (CO) and hydrogen cyanide (HCN)from N containing materials) will be much greater.
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