polyurethane foam, when burned gives off

The guidelines above for choosing a safer mattress or non toxic mattress topper can help determine which . In addition, asphyxiation can also occur as a result of lowered oxygen concentration, and is affected by the carbon dioxide concentration. The difficulty of replicating the conditions of fully developed under-ventilated flaming on a bench-scale is caused by several practical problems. Studies have found that infant mattressesespecially those made with polyurethane foam, which contains the hydrocarbon tolueneare a major off-gassing culprit (Boor, et. Very few authors have assessed the yields of isocyanates produced during the flaming combustion of polyurethane foams and as such there is a limited amount of data available. FEC model from ISO 13571. However, PVC will typically not burn once the source of heat or flame is removed. Equation 2 calculates the FED of the major asphyxiants, CO and HCN, but without taking oxygen depletion or CO2 driven hyperventilation into account. The radiant heat apparatus, smoke chamber and controlled atmosphere cone calorimeter produced much lower CO yields than would be expected for under-ventilated flaming. 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. Polyurethanes are a diverse family of synthetic polymers that were first synthesised in 1937 by Otto Bayer. Combustion and Flame 146(12):p95108, Rogaume T, Bustamante-Valencia L, Guillaume E, Richard F, Luche J, Rein G, Torero JL (2011) Development of the Thermal Decomposition Mechanism of Polyether Polyurethane Foam Using Both Condensed and Gas-Phase Release Data. Polyurethane and polyisocyanate both release polyols and isocyanates during blowing, but the rates diminish rapidly over time as the product cures, provided they dialed in the temps & chemical mix correctly. The formation of HCN was at a higher temperature in both air and nitrogen (400C and 550C respectively) with an average concentration of 200ppm at 500C. As the main reactive group that isocyanates react with, polyols are a major component of the resulting polyurethane product. The smoke density chamber (ISO 5659-2) showing a sampling probe for fire smoke toxicity. In both rigid and flexible foams, aniline and p-aminotoluene were reported, which correlates with the work of Ravey and Pearce (1997) who reported that isocyanates that did not volatilise were converted into amines in the condensed phase. When the black char was burned at 600C, it yielded 14.95mg of HCN (65mg per gram of char) and the yellow oil yielded 21mg per gram of oil. (2007) suggests that their yields are not heavily dependent on the ventilation conditions and that the yields would likely only increase by a small amount during under-ventilated flaming. (1990) also reported increased HCN yields when the sample was allowed to smoulder before flaming in similar apparatus as above. decomposition products will burn. Polyurethane. The foam could be cleaned and a coating or metal cladding could be installed over it. Their analysis indicated that, above 600C, the high temperature decomposition of MDI generated a large number of volatile fragments, including benzene, toluene, benzonitrile and toluonitrile. This amine may then undergo further reaction with other isocyanates present to produce a urea (Scheme3). Over 90% of all industrial polyurethanes are based on either TDI or MDI (Avar et al. When a one gram sample of foam was decomposed in air, CO was formed at a lower temperature than in nitrogen (300C vs 400C), with a relative concentration of 5000ppm at 500C. Polyurethane foam insulation is a superior insulator with high RValue. 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. Results from these burn tests are used for comparison with the model developed to simulate flame spread, heat fluxes, and smoke development over time (Figure 1). The authors presented a large set of data for all of the test methods, including a range of test conditions, air flow rates, oxygen concentration, and mass loadings. 10. Similarly to the trend reported by Stec and Hull (2011) in well-ventilated conditions, this can be attributed to gas phase free radical quenching in the material by the chlorine present in both the CMHR-PUF and PIR (2.53% and 3.56% chlorine by weight, respectively). The toxic effect of carbon monoxide is characterised by a lowered oxygen-delivery capacity of the blood, even when the partial pressure of oxygen and the rate of blood flow are normal. Conversely, nitric oxide gas at low concentrations(~20 ppm) has been used to aid breathing in the treatment of respiratory disorders (Kavanagh & Pearl 1995). Int Anesthesiol Clin 33:181, Kimmerle G (1976) Toxicity of Combustion Products with Particular Reference to Polyurethane. As polyols are prepolymers, their molecular mass is relevant to their application, with flexible foams being derived from 1000 to 6000 daltons and few hydroxyl groups, while those used in rigid foams have short chains from 250 to 1000 daltons with high functionality (312 hydroxyl groups per chain). However, instead of finding my answer I found seemingly endless reports on websites claiming that memory foam gives off potentially toxic fumes. The Steady state tube furnace apparatus, ISO/TS 19700. Smouldering was forced by an electrically heated resistance wire embedded in the sample and a load cell measured the mass of the sample throughout the experiment. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme5). 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). Both of the materials showed a clear relationship with the HCN yield increasing with . However, as fires tend to grow exponentially, they do not produce constant concentrations of asphyxiant gases. HCN, in particular, contributes significantly to the overall fire toxicity of polyurethane foams. . 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. In a real fire, involving cycles of growth and decay of flaming combustion, the resulting yields of HCN from the combustion of polyurethane foams are likely to be higher than predicted in some bench-scale methods as a result of this two-step decomposition mechanism. It can be used for testing samples 100100mm and up to 50mm thick, in both the horizontal and vertical orientation. 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. This is due to the large range of available fire retardants found in polyurethane foams, which suggests that the toxicity will likely follow the general trends in the literature for all materials regarding fire retardants. 2 The results indicated that the formation of the precursor, TDI, was much faster and preferable to depolymerisation when the volatile compounds could escape. The CACC and SDC show reasonable agreement for well-ventilated burning, but fail to replicate the more hazardous under-ventilated fire conditions. 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. A polyether polyol (i) and a polyester polyol (ii). The results from the SSTF and FPA show the best agreement with those from the full and 1/3 scale ISO room for both materials under a range of fire conditions. Paabo and Levin (1987) reviewed the literature of the toxic product generated by the combustion of rigid polyurethane foams. The protocol has been modified as a toxicity test by the mass transport industries, in the aircraft (EN 2826 2011), maritime (Fire Test Procedure Code 2010), and railway tests (CEN/TS 455452 2009). The reaction of an isocyanate functional group with water (Scheme2) results in the formation of an unstable carbamic acid group, which in turn decomposes to release an amine and carbon dioxide. statement and 2007). April 30, 2021 April 16, 2021 by Shobita Ravichandran. 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 widespread use of flexible polyurethane foams in furniture and other upholstery, where they are usually covered in some kind of fabric has prompted some authors to investigate the effects of covering the foam on the yield of toxic products. Babrauskas V, Lawson JR, Walton WD, Twilley WH (1982) Upholstered Furniture Heat Release Rates Measured with a Furniture Calorimeter. Polyurethane foam may be formed at a construction site or installed in the form of board stock (see the "Composite Insulations, Structural Insulated Panels" section). Since HCN is a major contributor to the fire toxicity of polyurethane foams, the mechanisms by which they decompose are vital in understanding why they produce large-quantities of HCN during under-ventilated burning. An FED equal to one indicates that the sum of concentrations of individual species will be lethal to 50% of the population over a 30min exposure. When a liquid fuel gives off enough vapors so that it can be . Polyurethane is widely used, with its two major applications, soft furnishings and insulation, having low thermal inertia, and hence enhanced flammability. The steady state tube furnace produced a CO yield that was closer to what would be expected for under-ventilated conditions. Prog Energy Combust Sci 21:197237, Purser DA (2002) Toxicity Assessment of Combustion Products, The SPFE Handbook of Fire Protection Engineering 3rd Edition, Edited by DiNenno, P.J. NBSIR 822532. (1999) used the controlled atmosphere cone calorimeter, but argues correctly,in the authors' opinion,that an instantaneous effective global equivalence ratio The reported yields were extremely low for both CO and HCN, as the NBS smoke chamber apparatus is a well-ventilated fire scenario reported to give low HCN yields (Table6). ISO 19706 (2011) Guidelines for assessing the fire threat to people. One analysis of fire victims' blood showed a trend of declining COHb and a rise in cyanide concentrations (Anderson et al. 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. Does the foam give off toxic fumes if burned? The authors would like to thank Dr. Linda Bengtstrom for her contribution regarding the toxicity of isocyanates. In a report from the same laboratory, Braun et al. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. This causes deterioration in mental and muscular performance. The specific mass of the polyurethane sample was not provided by the author and the ventilation conditions were not clear as a result of this. 2013). However, the presence of Cu2O reduced the HCN generated by the flexible polyurethane foam by 70-90% at low temperatures. New memory foam smell? 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. 11) ultimately giving well-ventilated flaming. The two main market uses for polyurethane are in the furniture and interior industry and the construction industry with 28% and 25% of the market, respectively (Markets & Markets report 2011). A sample of rigid polyurethane foam was heated in a static tube furnace with an air flow of 50mlmin1 at a range of temperatures from 600 to 1200C and the yield of HCN was quantified. Other common diisocynates include hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI) and isophorone diisocyanate (IPDI) (Fig. The higher flammability of these new furniture products took people by surprise, and has been blamed for an increased number of serious fires and a tripling of fire deaths over 20years (Fig. The FED value is calculated using the exposed dose relationship (concentration-time product, Ct) for CO. The yields of toxic products followed the expected trend of being higher in the under-ventilated conditions. EN 2826. This range of functional groups and their ratios in the polymer are a large contributing factor to the wide range of properties that polyurethane materials can possess. Preliminary calculations suggested that 27% of the TDI should be recovered as DAT. These processes occur at around 300C with the precursor chemicals including TDI, MDI, HDI, polyols (both polyether and polyester-polyols) and aromatic amines. The presence of oxygen in the atmosphere directly interacts with the solid phase, which accelerates decomposition. 1982) to that of a large scale test room. 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. Causes of UK fire deaths from 1955 to 2013 (UK Fire Statistics 2013). (1991b) wherein polyurethane containing a phosphate fire retardant caused immediate death of all of the animals. 2008) and is 40kWm2 in the centre of the furnace at 650C and 78kWm2 at 825C. 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. The main toxic combustion products can be divided into two classes: asphyxiant gases, which prevent oxygen uptake by cells, with loss of consciousness and ultimately death; and irritant gases which cause immediate incapacitation, mainly by effects on the eyes and upper respiratory tract, and longer term damage deeper in the lung. (2007)), the sample is raised to a fixed furnace temperature, which is further increased in the gas phase during flaming combustion. Thermal Decomposition of Polyether-based, Water-blown Commerical type of Flexible Polyurethane Foam. The review suggested that the addition of fire retardants did not appear increase the overall combustion toxicity of polyurethane foams. Aromatic diisocyanates ortho- or para- to one another will have an activating effect on each other, thus increasing their reactivity. The three compartments were connected by doors and the target room contained an open vent. 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. FED model from ISO 13571, Equation While there were some problems, the data does show that the yields of toxicants from the polyurethane foam were generally most representative of post-flashover conditions in the test methods that were designed for ventilation controlled conditions, such as the steady state tube furnace and the controlled atmosphere cone calorimeter. 2023 BioMed Central Ltd unless otherwise stated. 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. In the smoke chamber, the highest reported yield during flaming combustion was 1.02mgg1. While it is evident that the HCN yield increases as a fire becomes more under-ventilated, the link between the nitrogen content of the fuel and the yield of HCN is less clear. When =1 the theoretical amount of air is available for complete combustion to carbon dioxide (CO2) and water. Carbodiimides are produced by the reaction of isocyanates in the presence of a catalyst (such as phospholine oxides) (Scheme8) (Avar et al. Fire Science Reviews Fire Technology 51:p318, Blomqvist P, Lonnermark A (2001) Characterization of the combustion products in large-scale fire tests: comparison of three experimental configurations. In others, under reduced oxygen concentrations, the fuel lifts from the surface, but ignition does not occur (Christy et al. 1986). Further to this, a similar pattern began to emerge in the injuries of fire victims (Fig. The author acknowledged that there is a range of contradictory results available in the literature regarding their fire toxicity. Spray Foam Insulation: Helping Achieve Sustainability.