DiNenno) Fourth Edition. A comprehensive review of fire retardants and their use in polyurethane foams was published by Singh and Jain (2009). 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). MDI is a diaromatic diisocyanate compound that boils at 208C and is primarily used in the production of rigid foams. Alongside the experiments performed in the steady state tube furnace, the PIR was also investigated in a half scale ISO 9705 room-corridor test and in a full size ISO 9705 (1993) room. The polyurethane market was estimated to be worth $33 billion in 2010 and is expected to continue to grow to over $55 billion by 2016. These substances can include carbon dioxide, carbon monoxide, formaldehyde, aldehydes, and other volatile organic compounds (VOCs), as well as soot and particulates. the sum of each of the concentrations multiplied by the exposure time, for each product; upper respiratory tract irritants are believed to depend on the concentration alone (Purser 2007). While this may occur to some degree, it is generally accepted that the majority of the diisocyanates produced in the decomposition of polyurethanes are either volatilised or converted into their amine derivative and then volatilised. Michal (1982) reported a similar trend at a fixed air flow rate. 10. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). 13) (UK Fire Statistics 2013). This equation only relates to lethality, or cause of death. When tested with the polyester covering the polyurethane, the yield of HCN during flaming combustion was higher than that of just the polyurethane foam on its own. Toxicology 47:165170, Kaplan HL, Grand AF, Hartzell GE (1984a) Toxicity and the smoke problem. To a lesser extent, parameters such as temperature and oxygen concentration also affect the yields of toxic products. 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)). 1982), the authors exposed male Fisher 344 rats in a 200L exposure chamber to the fire effluent from the flaming and non-flaming combustion of both materials. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. For both materials there is a clear increasein yield from the well-ventilated to under-ventilated conditions. The dimerisation of two isocyanates is a reversible reaction that produces uretidione ring (Scheme6). Diesel engines use the principle of _____ to ignite fuel vapor. Rigid polyurethanes primarily produced aromatic compounds in the condensed phase products of decomposition, whereas flexible polyurethanes produced aromatics, alcohols, aldehydes and heterocycles. The sample is spread evenly in a silica boat over a length of 800mm and fed into a tube furnace at a typical rate of 1gmin-1 with flowing airat a rate of 2-10 L min-1. The samples tested included both commercial rigid polyurethane foam and polyisocyanurate foam. Based on this data, the HCN recovery fraction was calculated for both materials. National Fire Protection Association, Quincy, pp 283, Purser DA (2007) The application of exposure concentration and dose to evaluation of effects of irritants as components of fire hazard. 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 relationship between equivalence ratio and yields of CO and other products has been studied in detail for a wide range of materialsduring flaming combustion using two small-scale apparatus designed specifically for this purposethe ASTM E2058 fire propagation apparatus (Tewarson 2002) and the ISO/TS 19700 tube furnace apparatus (ISO/TS 19700 2013), in conjunction with a series of large-scale experiments used for validation (Gottuk & Lattimer 2002; Blomqvist & Lonnermark 2001; Purser & Purser 2008a). 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. 1). But many products or materials continue off-gassing even after the "new smell" has gone awaythe fumes are just much more subtle. 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 results showed a HCN yield of 15.8mgg1 at 600C. The first being a depolymerisation which would dissociate the polymer to isocyanates and alcohols, the second being dissociation to a primary amine, an olefin and carbon dioxide. This causes deterioration in mental and muscular performance. Isocyanates are a highly reactive family of compounds that are characterised by the RN=C=O functional group (where R can be any aliphatic or aromatic functionality). The most widely used fire-test apparatus, stipulated in smoke regulations in most countries of the developed world, is the smoke density chamber as described inISO 56592 2012, andshownschematically in Fig. Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. 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. STM wrote the manuscript and produced all of the images used in figures. Fire and Materials 19:p6164, Shufen L, Zhi J, Kaijun Y, Shuqin Y, Chow WK (2006) Studies on the Thermal Behavior of Polyurethanes. National Bureau of Standards, Washington D.C. Levin BC, Paabo M, Fultz ML, Bailey C, Yin W, Harris SE (1983a) Acute inhalation toxicological evaluation of combustion products from fire-retarded and non-fire retarded flexible polyurethane foam and polyester. Its widespread availability has encouraged its adaptation to toxic gas generation and assessment. Chem Co., Dow, Hertzberg T, Blomqvist P, Dalene M, Skarping G (2003) Particles and Isocyanates from Fires. 2008) and is 40kWm2 in the centre of the furnace at 650C and 78kWm2 at 825C. In the chamber, 0.23g of black char and 0.04g of yellow oil were recovered. Thermosets are cross-linked polymer molecules which, on heating, do not melt but will eventually decompose. The full size ISO 9705 test resulted in well-ventilated flaming ( 0.260.5) due to the relatively large volume of air and relatively small sample size. Rubber Chemistry and Technology 32(2):p337345, Article The fire toxicity of polyurethane foams. 23. Self-addition reaction of two isocyanates to produce a uretidione, Self-addition reaction of three isocyanates to produce a isocyanurate ring, Reaction of two isocyanates to produce a carbodiimide. Over short periods, inhaled CO impairs an individuals ability to escape, causing different effects at different concentrations. This amine may then undergo further reaction with other isocyanates present to produce a urea (Scheme3). The non-flaming decomposition of non-fire retarded polyurethane foams in air is generally quite well understood and comparable to the inert atmosphere decomposition, in terms of both products and mechanisms. Common polyurethane functional groups i) urethane ii) urea iii) carbodiimide iv) uretdione v) isocyanurate. Terence Richard Hull. However, once one of the groups forms a urethane or urea, the activating effect on the other isocyanate is reduced, as ureas and urethanes are weaker activating groups than isocyanates. Babrauskas et al. The author acknowledged that there is a range of contradictory results available in the literature regarding their fire toxicity. Both may be present in fire effluent, for example from PVC or halogenated flame retardants, and since the damage caused by the acidity (the concentration of H+ ions) is independent of the specificanion (Cl or Br), the discussion on HCl is also applicable to HBr. The steady state tube furnace (ISO/TS 19700 2013), shown in Fig. Over this period there was a corresponding shift from the main cause of death in fires being attributed to burns to being attributed to inhalation of smoke and toxic gases. In China and Japan, there are specific restrictions on the use of materials with high fire toxicity in high risk applications such as tall buildings, while an increasing number of jurisdictions permit the alternative performance based design approaches to fire safety. 8 and Table3. 1984a). Int Anesthesiol Clin 33:181, Kimmerle G (1976) Toxicity of Combustion Products with Particular Reference to Polyurethane. Fire and Materials 5(4):p133141, Christy M, Petrella R, Penkala J (1995) Controlled-atmosphere cone calorimeter. During these tests, the PIR was set up as wall panels covered on two faces with aluminium foil. 6). Material composition, temperature and oxygen concentration are normally the most important. In a compartment fire, the reactions of under-ventilated flaming occur in both the flame zone and in the hot upper layer. More recent work by Shufen et al. However, spray foam insulation is a highly energy-efficient product and quickly offsets its manufacturing footprint. California Privacy Statement, Secondary air is added in a mixing chamber to give a total gas flow of 50Lmin1. (such as polyurethane foam) burn slower (have a lower (HRR) than higher-density materials (cotton padding) of similar makeup. p 1-30. The PIR foam produced similar HCN yields to the CMHR-PUF until 1.5, after which it increased more rapidly to give a yield of 20mgg1 at ~1.75. An equation has been developed for the estimation of the FED for lethality from the chemical composition of the environment in the physical fire(such as the bench-scale methods described in the following section) model taken from ISO 13344 (1996) and uses gas-LC50 values for lethality to provide referencetoxicity data for the individual gases to calculate toxic potency, based on rats exposed for 30min. The authors acknowledged that they did not include isocyanates in their calculations. The revised protocol is based on continuous sampling of the fire effluent. Garrido and Font (2015) reported two main steps in the inert-atmosphere decomposition of flexible polyurethane foams. Toxicology 115:7, Henneken H, Vogel M, Karst U (2007) Determination of airborne isocyanates. The most commonly reported adverse health effects after airborne isocyanate exposure is asthma due to sensitisation (Piiril et al. Biurets are the result of the reaction of isocyanates with substituted-urea functional groups and allophanates are formed in small amounts (unless catalysed) by the reaction of isocyanates with urethanes. HCN yields reported in under-ventilated conditions vary depending on the composition of the material; with flexible foams producing less than rigid foams and polyisocyanurates producing the most overall. At this temperature around one third of the compounds mass was lost as volatile products, and the regenerated alcohol products were mainly present in the residue of the sample. In some bench-scale apparatus the heat flux is constant, and often insufficient to sustain flaming at such low oxygen concentrations; further, an unknown quantity of fresh air bypasses the fire plume, so the ventilation condition, and hence, remains undefined. Syntheticpolymeric materials may be divided into thermoplastics and thermosets. In this modification, the controlled atmosphere cone calorimeter (CACC) (Babrauskas et al. (1981) on polycarbodiimides and polyureas enabled the determination of the source of the organonitriles and HCN during thermal decomposition. Free of VOCs and HAPs. The first is by combination with the ferric ion in mitochondrial cytochrome oxidase, preventing electron transport in the cytochrome system and inhibiting the use of oxygen by the cells. Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. Fire Safety Journal 40:439465, Aneja A (2002) Chapter 2, Structureproperty Relationships of Flexible Polyurethane Foams, PhD. Burning foam will emit mainly carbon monoxide, carbon dioxide and small traces of other toxic gases, such . Journal of Fire and Materials 4:p5058, Farrar DG, Hartzell GE, Blank TL, Galster WA (1979) Development of a protocol for the assessment of the toxicity of combustion products resulting from the burning of cellular plastics, University of Utah Report, UTEC 79/130; RP-75-2-1 Renewal, RP-77-U-5. Routes of entry in this case are inhalation, ingestion (saliva), and skin absorption. A summary of these structures is shown in Fig. Isocyanate structure also affects the reactivity of the isocyanate group. Journal of Applied Polymer Science 111:p11151143, Stec AA, Hull TR (2011) Assessment of the fire toxicity of building insulation materials. al, 2014). Woolley WD, Fardell PJ, Buckland IG (1975) The Thermal Decomposition Products of Rigid Polyurethane. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. Purser model, [AGI] is the concentration of inorganicacid gas irritants, [OI] is the concentration of organic irritants, A is an acidosis factor equal to [CO2]0.05. The peak HCN value reached was 10mg per g1 in the under-ventilated tests. The cone calorimeter (ISO 56601 2002) is probably the most widely used apparatus for measurement of flammability properties such as ignitability and heat release rate (Schartel & Hull 2007). CORE - Aggregating the world's open access research papers They also asserted that the toxicity of the fire retarded foam was less than or equal to wood on a mass/mass basis and that wood contributes significantly more to residential fires in terms of fire smoke toxicity. The authors reported GC/MS analysis of the condensed phase products obtained. Despite their name, the term polyurethane is used to describe a family of polymers whose monomers are joined by a range of functional groups primarily derived from the polyaddition of polyisocyanates and polyalcohols. Journal of Analytical and Applied pyrolysis 113:p202215, Gharehbagh A, Ahmadi Z (2012) Chapter 6: Polyurethane Flexible Foam Fire Behaviour, Polyurethane. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. Several authors have investigated the relationship between bench-scale test data and large-scale test data using polyurethane foams. Brit Polym J 1:p203204, Braun E, Gann RG, Levin BC, Paabo M (1990) Combustion product toxic potency measurements: comparison of a small scale test and real-world fires. At 1000C the hydrogen cyanide produced accounted for a range of between 3.8 and 7.3% by weight. The trimerisation results in a highly stable isocyanurate ring which confer additional thermalstability to polyisocyanurates (Scheme7). As fires grow, they become ventilation controlled, and fires in enclosures such as buildings rapidly change from well-ventilated to under-ventilated. Nitric oxide (NO) and nitrogen dioxide (NO2) are non-flammable gases present in fire effluents. (1991a) compared a number of test methods. 2 (Avar et al. A detailed understanding of the thermal decomposition chemistry of polyurethane foams is necessary in order to relate the toxicants generated during bothflamingand non-flaming combustion of the polymer to its structure. Irritant gases cause pain and breathing difficulties, leading to incapacitation, such that the victim can no longer effect their own escape (ISO 13571 2012). However, the yield of CO was lower in both the non-flaming and flaming combustion. Before you take it for a test drive, make sure to give your new mattress time to off-gas in a well-ventilated environment. Taking into consideration the issues with repeatability of large-scale testing, the authors asserted that the similar trend in HCN yields supported the good relationship between the tube-furnace and large-scale results. The authors associated this with the effects of the Cu2O catalytically oxidising the HCN into N2, CO2, H2O and a small amount of nitrogen oxides. At 650C, the yield of HCN from the CMHR-PUF increased up to ~2.0 where it reached a peak of 14mg of HCN per gram of polymer burned. Using polyurethane indoors can expose you to fumes with a number of potential side effects. The radiant heat flux in the ISO/TS 19700 apparatus has been measured (Stec et al. Heat, smoke and irritant gases may impair escape, increasing the risk of a lethal exposure to asphyxiant gases, andcan sometimes lung damage causes death in those managing to escape. The authors noted no significant difference in the range of yields of isocyanates detected in either well- or under-ventilated conditions with a range of 1.0-1.6mgg1. 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. Unfortunately, your body heat appears . Using the methodology in ISO 13344, the authors also calculated the fractional effective dose (FED) of the individual toxicants sampled. The yields of CO and HCN at varying and temperature are presented in Table5. 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). In general conversion efficiencies are high for halogen acid gases. Avar G, Meier WU, Casselmann H, Achten D (2012) Polymer Science: A Comprehensive Reference, Polymer Science: A Comprehensive Reference, 10, p411-441. The non-flaming decomposition of polyurethanes in air or nitrogen can be summarised effectively usinga generalised mechanism based on the available literature (Fig. The yield was much lower at 800C with 7.4mgg1 but at 1000C and 1200C the yield increased significantly to 33.9mgg1 and 48.1mgg1 respectively. It can be used for testing samples 100100mm and up to 50mm thick, in both the horizontal and vertical orientation. TDI is produced as the 2,4- and the 2,6- isomer which have a boiling point of 121C and 120C respectively. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. At ~2.0 the CMHR-FPUR resulted in 8% and 11% nitrogen recovered as HCN for 650C and 850C respectively. The severity of the effects increases with dose (Hartzell 1993). The test conditions were designed so that the fire conditions met the ISO 19706 (2007) fire type 2 (well-ventilated flaming fire <0.75) and fire type 3b (post-flashover fire in large or open compartments ~2.0). In ventilation controlled fires (such as those occurring in a room, buildingor other enclosure), the yields of these gases from the flaming combustion of polyurethane foams generally follow the same trend. However, when >2.0 the yield of HCN decreased, falling to 10mgg1 at ~2.75. Additionally, a polyol-rich residue is left behind that begins to fragment and volatilise between 300 and 600C. The authors noted that the total concentrations of CO and HCN during flaming combustion were greater than the sum of those from the individual materials.
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