Polymer-Plastics Technology and Engineering 45:p95108, Singh H, Jain AK (2009) Ignition, Combustion, Toxicity, and Fire Retardancy of Polyurethane Foams: A Comprehensive Review. The general approach in generating toxic potency data from chemical analysis is to assume additive behaviour of individual toxicants, and to express the concentration of each as its fraction of the lethal concentration for 50% of the population for a 30min exposure (gas-LC50). 2 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. This makes the isocyanate functional group highly reactive towards nucleophiles with an available hydrogen. In most countries, there are no regulations covering the fire toxicity of building components, or for most road vehicles, including goods vehicles in tunnels. Insulation, like all building products, has an 'embodied' carbon footprint resulting from energy use during the manufacturing process. \( \phi =\frac{actual\; fuel\;to\; air\; ratio}{stoichiometric\; fuel\;to\; air\; ratio} \). The lowest temperature at which a liquid will give off vapors at a sufficient rate to support a momentary flame across its surface is known as its: . 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. The polyester based polyurethane began to decompose at 284C with a secondary decomposition step at 359C. Suggested points of chain scission on a polyether polyol resulting in aldehydes, ketones and alkenes (Allan et al. 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. The reaction of a urethane with another isocyanate will produce an allophanate (Scheme 5). The study also suggested that any remaining isocyanates residue would react with themselves to produce polycarbodiimides, thus anchoring the isocyanate precursors in the condensed phase until around 600C, where they would fragment. In: Fahima Z, Eram S (eds), InTech. Most rigid foams and speciality polyurethanes use polymeric MDI derivatives which are mixtures components such as dimers and trimers (Fig. The methods of assessment of fire toxicity are outlined in order to understand how the fire toxicity of polyurethane foams may be quantified. In an attempt to improve the understanding of the thermal decomposition of polyurethanes, Rogaume et al. Hexamethylene diisocyanate (HDI) (i), 1,5-naphthalene diisocyanate (NDI) (ii) and isophorone diisocyanate (IPDI) (iii). This was observed by Levin et al. Preliminary calculations suggested that 27% of the TDI should be recovered as DAT. Relation of LC Both of the materials showed a clear relationship with the HCN yield increasing with . In a series of investigations, Purser and Purser (2008a) examined the yields of HCN from a range of materials and the conversion of fuel nitrogen to HCN. 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. The yields of CO and HCN from five bench-scale methods have been compared to large-scale data under a range of flaming fire conditions (Stec & Hull 2014). During polymerisation, isocyanates undergo a number of distinct reactions. Gaithersberg, MD, Babrauskas V, Twilley WH, Janssens M, Yusa S (1992) Cone calorimeter for controlled-atmosphere studies. Taking this into consideration, the reported yields of isocyanates, aminoisocyanates and amines are still relevant, as the results of Blomqvist et al. Thermoplastics are composed of linear polymer molecules, whose shape can be changed repeatedly on heatingand which may be melted and solidified without chemical change. 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. 1984a). These substances can include carbon dioxide, carbon monoxide, formaldehyde, aldehydes, and other volatile organic compounds (VOCs), as well as soot and particulates. New memory foam smell? 2008), where inhaled isocyanates rapidly form conjugates with epithelial lung cell proteins (Wisnewski et al. 2012). Med Sci Law 21:60. The PIR at 1.75 resulted in 15% of the fuel nitrogen being recovered as HCN. However, in the field of combustion toxicity testing, this under-ventilated burning is the most difficult to create using bench-scale apparatus. This suggests that any amines formed would have reacted with isocyanates in the vapour phase to form ureas, some of which would have condensed to produce the observed waxy white substance. For the purpose of estimating toxicity in fires, fire growth has been classified into a number of stages (ISO 19706 2011): Although on some occasions smouldering (oxidative pyrolysis) can generate toxicologically significant quantities of effluent (for example smouldering cotton, or polyurethane foam), typicallythe rate of reaction, and hence the amount of toxic species generated will be small, so it is unlikely to affect anyone outside the immediate vicinity. The formation of the toxicant in question was the result of an unusual reaction of the polyol in the foam, trimethylol propane, with the phosphate fire retardant in the gas phase. . Ann occup Hyg 19:269273, Levchik SV, Weil ED (2004) Thermal Decomposition, combustion and fire-retardancy of polyurethanes - a review of the recent literature. 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. Foam: Fire Hazard and Fire Barrier | Monolithic.org (2006) has supported the claim that polyether based polyurethanes are less stable than their polyester based counterparts when decomposed in air. 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. Additionally, the authors reported a yield of 1315mgg1 of CO, 1.41.5mgg1 of HCN, and 1012mgg1 of NO. Performing hot work on or near polyurethane foam may lead to potential exposures to isocyanates and other toxic emissions. The difference with other polyurethane foams is that memory foam also contains added chemicals that increase its viscosity and elasticity, hence its alternate name, viscoelastic foam. The samples were heated at 800C in a static tube furnace, with the effluent being cooled to <50C before entering an exposure unit. Thermal Decomposition of Polyether-based, Water-blown Commerical type of Flexible Polyurethane Foam. 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. This results in relativelyhigh yields of CO and HCN during under-ventilated flaming and relatively low yields during well-ventilated flaming. (1985) when a flexible polyurethane foam was first heated at a temperature below its auto-ignition temperature, followed by flaming combustion of the remaining char and residue at a higher temperature. At high concentrations these acids can cause pulmonary oedema and death (Paul et al. Journal of Analytical and Applied pyrolysis 108:p143150, Hartzell G (1993) Overview of Combustion Toxicology. 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. 4). As a result of this, studies that use ventilation controlled conditions, such as those using the steady state tube furnace (ISO/TS 19700 2013), are more likely to give a realistic representation of these reduced oxygen environment fire conditions. Furniture, upholstery and curtains Polyurethane foam when burned gives off - wiehoch.com In a compartment fire, the reactions of under-ventilated flaming occur in both the flame zone and in the hot upper layer. thesis, Virginia Tech, p6-40, ASTM E 1354 Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter, ASTM E 662 Standard Test Method for Specific Optical Density of Smoke Generated by Solid Materials. Off-gassing & Outgassing: What's the Difference? Where is it From What does polyurethane foam give off when burned? Isocyanate structure also affects the reactivity of the isocyanate group. 2023 BioMed Central Ltd unless otherwise stated. VOCs and Other Toxic Chemicals in Mattresses: What to Know 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. The overall toxicity of the polyisocyanurate foam shows a clear increase as the fire became more under-ventilated, while the rigid polyurethane foam showed a slight decrease at 1.242.00.