Fire and Materials

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Online ISSN: 1099-1018
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Chapter
This paper presents the findings of the NIST World Trade Center Investigation describing the occupant evacuation of WTC 1 and WTC 2 on September 11, 2001. The egress system, including stairwells and elevators, is described along with the evacuation procedures. The population in WTC 1 and WTC 2 on September 11, 2001 at 8:46 a.m. is enumerated and described, where the background of the population was relevant to the subsequent evacuation, including training, experience, mobility status, among others. The progress of the evacuation of both towers is described in a quasi-chronological manner. A decedent analysis explores where occupants were located when each tower was attacked. Multiple regression models were built to explore the sources of evacuation initiation delay (why people did not immediately start to leave the building), as well as stairwell evacuation time (how long the average occupant spent in the stairwells per floor). Issues identified as contributing to either slowing or aiding the evacuation process were explored. Egress simulations provided context for estimating how long WTC 1 and WTC 2 would have taken to evacuate with different populations, using three different models, and subject to different assumptions of damage to the building.
 
Article
Relative toxicity test data on 270 materials are presented, based on test procedures developed at the University of San Francisco. The effects of chemical composition, using data on 13 types of synthetic polymers and eight types of fabrics, are discussed. Selected materials were evaluated using nine test conditions with the USF method, and using methods developed at the FAA Civil Aeromedical Institute, Douglas Aircraft Company and San Jose State University.
 
Article
Different types of floor coverings were tested using three different methods: the Cone Calorimeter (ISO 5660), the Nordtest floor covering test NT FIRE 007 and the German Radiant Panel Method (DIN 4102 Teil 14). The results of the comparisons between both flame spread and smoke production are given. Some correlation is found between the results of the Cone Calorimeter and the NT FIRE 007. Between other methods, no correlations seem to exist.
 
Article
The Fourier Transform infrared spectrometer method is developed by VTT Fire Technology in Finland, and is described by NORDTEST as NT FIRE 047. The method takes gas samples from the ventilation duct of a cone calorimeter, and is used to perform dynamic quantitative or qualitative measurements. This is an important step in the direction of continuous measurements of gas components in fire smoke. A lot of effort, knowledge and funds are required for a proper calibration and use of this equipment. The experience with application and interpretation of the test method is reviewed in regard to mounting, calibration and use of the equipment. The work concludes that the NORDTEST NT FIRE 047 test method needs to be revised and completed in the sections on apparatus, calibration routines, analysis procedure and expression of results. The missing information and details can lead to differences in application of the method. Until a revised document appears, frequent communication between laboratories can eliminate these differences.
 
Article
This paper briefly describes the methodologies employed in the collection and storage of first-hand accounts of evacuation experiences derived from face-to-face interviews with evacuees from the World Trade Centre (WTC) Twin Towers complex on 11 September 2001 and the development of the High-rise Evacuation Evaluation Database (HEED). The main focus of the paper is to present an overview of the preliminary analysis of data derived from the evacuation of the North Tower with an emphasis on frequency of occupant stoppages on stairs, occupant stair travel speeds and occupant response times. The paper also describes some of the evacuation modelling analyses of the evacuation of the North Tower undertaken as part of project HEED. Copyright © 2011 John Wiley & Sons, Ltd.
 
Article
This paper describes a survey which was undertaken to ascertain those features of house design and construction which were important to the survival of house in the ‘Ash Wednesday Bushfires’ of 16 February 1983. The Otway Ranges are of Victoria was chosen and 1153 house, with varying degrees of damage, were included in the survey. Results of a preliminary analysis of data collected are given, together with observations made concerning the so-called ‘exploding house’ phenomenon, the role of wind and the part that people played in house survival. Evidence for the ways that houses were ignited (i.e. by radiation, flame contact and wind-blown embers) was also gathered. The importance of these ignition modes is discussed and examples given. Preliminary observations on the rebuilding process are also given.
 
Article
SUMMARYISO TS 19700 describes a test method for the generation of fire effluent and the identification and measurement of its constituent combustion products. The method has been previously accepted as a British Standard (BS 7990:2003) and as an IEC Standard (IEC 60695-7-50), which involves the decomposition of materials or products under various decomposing conditions occurring in different types and stages of real fires. It uses a moving test specimen and a tube furnace at different temperatures and air flow rates as the fire model. Simulations of flow and combustion conditions inside the tube (Purser) furnace were carried out and validated with the measurements. The objective of the present study is to demonstrate the validity of using computational fluid dynamics (CFD)-based fire field modelling techniques to predict the fire environment inside the tube furnace. These numerical investigations are also used to verify critical experimental operating parameters that affect the performance of the tube furnace and understand the modus operandi of the tube furnace toxicity method. Copyright © 2011 John Wiley & Sons, Ltd.
 
Article
The Fire Precautions Act 1971, in contrast with previous legislation, is directed exclusively to the provision of fire precautions in buildings after occupation. The system of control is by fire certificate and can be applied to a class of premise (listed in Section 1) by means of a designating order. In the case of any particular use of premise, the Secretary of State, under Section 12, may by Regulation, make provision as to precautions which are to be taken in relation to the risk to persons in case of fire.
 
Article
A study of fire deaths in the Glasgow area has been extended to the rest of the United Kingdom in order to assess the applicability of the conclusions reached in the Glasgow study to the whole country. With assistance from pathologists in a number of other areas, 71 cases were included in the study, covering both pathology and toxicology of the deaths where possible. In both the Glasgow and UK studies, most of the fire deaths occurred in dwelling-house fires. These and other demographic characteristics were in agreement with national fire statistics. The principal features of pathology in this study were burns (79 per cent of cases), respiratory system injury (72 per cent of cases) and soot deposition in the respiratory tract (96 per cent of cases), and these reflected a similar incidence in Glasgow study. Carbon monoxide was considered to be the cause of death in 51 per cent of the deaths in this study and to be implicated in the death of 37 per cent of the other cases (54 per cent and 31 per cent respectively in Glasgow). Cyanide was estimated to be a significant factor in 33 per cent of the deaths in the UK study (24 per cent in Glasgow). Alcoholic intoxication was found to be a significant additional factor in Glasgow but was much less prominent in the other areas of the UK. It concluded that, with the exception of alcohol, the results of the Glasgow study are valid for the UK as a whole.
 
Article
Recent development and trends of development in progress within the field of structural fire protection are described and evaluated with a focus on the contributions circulated within CIB W14. The presentation is structured on the one hand with regard to different methods of design (experimental determination of fire resistance, analytical determination of fire resistance, analytical design based directly or indirectly on real fire exposure characteristics), on the other with regard to different structural materials (steel, concrete and wooden structures). The presentation gives evidence of a development towards an increased application of analytical design methods based on modern structural safety philosophy. The urgency of increased research is stressed for improving the present building code systems in order to achieve fire safety levels which are consistent with strictly defined functional requirements.
 
Article
During the last twenty years a number design methods for calculating the movement of people in buildings have been developed. This presentation briefly reviews some of these modelling efforts. Furthermore, it discusses some aspects of the pedestrian movement and addresses an egress model based on the data provided by Predtechenskii and Milinski. This model is applicable to the evacuation of multi-storey buildings via staircases and predicts the flow movement in terms of time with regard to the building's layout and the interdependencies between adjacent egress way on this model, written in GWBasic language for any IBM-compatible personal computer. The program is built up as a dialogue between the user and the computer, where the escape route configurations (the width and the length of each section) as well as the number of the persons are put gradually during the course of the computation. The program enables the user to change the dimensions of the building's means of escape and the occupant load easily and work out the influence of the variation on the complete circulation system. Recently, the program also calculates the flow movement under decreased visibility conditions on smoke filled escape routes based on japanese measurements about the walking speed of pedestrians in fire smoke.
 
Article
This paper documents the first of the two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux, the motivation being that it has been reported that flame heat flux back to the burning surface in bench-scale experiments is not the same as for large-scale fires. The key aspect was the use of real scale applied heat flux up to 200kW/m2 which is well beyond that typically considered in contemporary testing. The main conclusions are that decomposition kinetics needs to be included in the study of ignition and the energy balance for steady burning is too simplistic to represent the physics occurring. An unexpected non-linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested and this non-linearity is a true material response. Using measured temperature profiles in the condensed phase shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes. The steady burning temperature profiles appear to be invariant with applied heat flux. This possible inaccuracy was investigated by obtaining the heat of gasification via the ‘typical technique’ using the mass loss flux data and comparing it to the commonly considered ‘fundamental’ value obtained from differential scanning calorimetry measurements. This comparison suggests that the ‘typical technique’ energy balance is too simplified to represent the physics occurring for any range of applied heat flux. Observed bubbling and melting phenomena provide a possible direction of study. Copyright
 
Article
The objective of this study is to directly measure the critical breakage stress for glass through mechanical tensile experiments based on MTS 810 apparatus. Two series of experiments were, respectively, conducted under the condition with a room temperature (25°C) and a hot environment (200°C) for float glass. The results show that the critical breakage stresses of 6, 8, 10 and 12 mm float glass are, respectively, 74, 127, 158 and 198% larger than that of 4 mm float glass under the condition with a room temperature (25°C). Similarly, the critical breakage stresses of 6, 10 and 12 mm float glass are, respectively, 29, 72 and 93% larger than 4 mm glass in the hot environment (200°C). In addition, through the comparison between the two series of experiments, it suggests that the critical breakage stresses of 6, 8, 10 and 12 mm thick float glass in a hot environment are, respectively, 7, 48, 16 and 19% smaller than that in a room temperature. It is suggested that the measured critical breakage stress of float glass here is relatively smaller than those in the previous measurements. Copyright © 2010 John Wiley & Sons, Ltd.
 
Article
The ASTM E-2058 fire propagation apparatus (FPA) is capable of measuring time to ignition, chemical and convective heat release rates, mass loss rate, smoke generation rate, generation rates of CO, CO2 and O2 consumption rate, effective (chemical) heat of combustion and vertical fire propagation of materials. The original design of the FPA incorporated a vertical exhaust system with the measurement section finishing about 3.5 m from the floor. The exhaust measuring duct of the new FPA is horizontally oriented to enable its use in a wider range of laboratory environments. In this paper, the functionality of the new FPA was compared with the original FPA. The measurements and results indicate that the performance of the new FPA is equivalent to the original FPA. Copyright © 2003 John Wiley & Sons, Ltd.
 
Article
A new bench-scale rate of heat release calorimeter utilizing the oxygen consumption principle has been developed for use in fire testing and research. Specimens may be of uniform or composite construction and may be tested in a horizontal, face-up orientation, or, for those which do not melt, in a vertical orientation. An external irradiance of zero to over 100 kW m−2 may be imposed by means of a temperature-controlled radiant heater. The rate of heat release is determined by measuring combustion product gas flow and oxygen depletion, while the mass loss is also recorded simultaneously. The instrument has been designed to be capable of higher accuracy than existing instruments and yet to be simple to operate and moderate in construction cost. The instrument is thermed a ‘cone calorimeter’ because of the geometric arrangement of the electric heater.
 
Article
A numerical study was undertaken to investigate the temperature field in steel joints and to compare the temperatures in the joints with the temperatures of the adjacent steel members on the hypothesis that the thermal protection is the same on the joint and in the members. Very brief information is given on the numerical model, supplemented with parametric studies made in order to determine the required level of discretization in the time and in the space domain. A simplified assumption for representing the thermal insulation is also discussed and validated. Different numerical analyses are performed, with a variation of the following parameters: (i) type of joints, from very simple to more complex configurations, with welds and/or bolts, all of them representing joints between elements located in the same plane; (ii) unprotected joints or protected by one sprayed material; (iii) ISO, hydrocarbon or one natural fire scenario. The fact that the thermal attack from the fire might be less severe because the joints are usually located in the corner of the compartment is not taken into account. Copyright
 
Article
This paper describes the use of advanced analysis that accounts for both material and geometric nonlinearity to assess the performance of steel structures exposed to a natural compartment fire. The advanced analysis is developed based on inelastic beam-column theory which can capture the ultimate strength behaviour of members for global analysis of large structures in fire. The heat transfer is computed using a refined finite element mesh. Compartment fire is simulated in accordance with the latest Eurocode prEN 1991-1-2. Performance-based assessments are carried out on multi-storey space frames subjected to a natural compartment fire. The computed results are compared with those from the conventional approach based on ISO standard fire curve and the advantage of the advanced analysis is highlighted. The effect of fire load and ventilation on the structural response of the frames is studied and the worst-case fire scenarios are identified. The design implications on the requirement of fire protection are discussed. Copyright © 2004 John Wiley & Sons, Ltd.
 
Article
Forest fires involve a wide range of unknown variables, e.g. wind flow over complex terrain, atmospheric stability, vegetation burning characteristics, location and fuel type, etc. The main objective of the present work is to incorporate the Rothermel simplified combustible model into a 3D unsteady flow solver appropriated for convective atmospheric flows over complex terrain. The released combustion energy is taken into account in the enthalpy equation. The unsteady byouant plume strongly influences the local wind speed direction and magnitude. A speical interactive coupling procedure was developed that links the calculated location of fire front and fire energy release to the momentum and energy transport for each time step. The general computer algorithm includes several other features such as the effect-drag of trees on the momentum transport and the consequent modifications in the k and ε turbulence model employed. The results include the prediction of fire development in flat terrain and in a valley and over hills covered by vegetation. A parametric study was conducted to detect the influence of wind speed, vegetation and fuel content on burning area, burning speed and wind speed direction.
 
Article
The behaviour of polymeric diphenyl methane-4,4′-diisocyanate (PMDI) is described when examined in a laboratory small-scale test for its reaction to fire (ease of ignition; heat release and toxic gas production). Full-scale real fire scenarios have also been staged to predict events if (1) drumstock PMDI and (2) sizeable pools of liquid PMDI become enveloped in a fire. PMDI requires a stimulus (e.g. heat) before it will ignite from an applied flame. It then burns in a self-sustaining manner for a few minutes, during which main emissions take place. Then a polymerization reaction begins, producing a low density non-burning residue, which progressively dampens down the burning events by blanket action. Residues of 30–80% sample weight were recorded. The major toxic gas produced is carbon monoxide, though free isocyanate is to be expected in the early stages of the fire, and hydrogen cyanide could be important, especially in well-developed fire conditions. Firefighters should therefore wear full protective clothing and fresh-air breathing equipment. Events when drums of PMDI are exposed to fire depend heavily on the characteristics of the containers, with some rupture steps proceeding with considerable violence. Drumstock PMDI should be stored separately from easily ignitable materials.
 
Article
A test chamber for performing complete investigation of the dangerous effects of thermal degradation products of polymeric materials has been designed. The tow-chamber system with separated combustion chamber and smoke chamber has a steep temperature gradient between both chambers and enables continuous analysis of combustion products of the tested polymeric material for carbon monoxide and carbon dioxide to be performed, to monitor the oxygen content in the chamber during testing and to perform tests of biological toxicity on mice as test animals. The function of the test chamber was verified on combustion of polyethylene, polypropylene, polystyrene and polyamide samples.
 
Article
An apparatus based on the BS 476 Part 7 small scale flame-spread specification, which has evolved over a number of years, is described. Many changes from the original simple gas/air furnace have been introduced, which have led to the development of a very useful flame-spread test apparatus where all known variables are precisely controlled. The work has shown that the radiometers described in the standard do not monitor all the variables which affect flame-spread results, and reported problems of reproducibility and variation on the large scale test, may be due to inadequate control of the furnace. The significance of the results is that the use of gas/air radian panels as the basis for flame-spread tests needs to be re-examined. All parameters should be carefully controlled and the entire procedure, particularly regarding the use of pilot ignition sources, needs to be reconsidered. There is an increasing need for test methods which assess materials at radiation intensities beyond that given by small ignition sources. The type of flame-spread apparatus described in the paper may help fulfil this important requirement.
 
Article
This work describes the results of an experimental study carried out in order to determine whether the combustion chamber CAB 650 can be used to determine the amount of heat released during combustion. The results of such tests would permit characterization of polymeric materials with respect to the three most important effects of fire - heat, smoke and the toxicity of the combustion products. A method has been developed enabling comparison of polymeric materials on the basis of the heat evolved during combustion. The calculated heat index yields information on the heat capacity of the material compared with cellulose as a standard material.
 
Article
An examination of the correlative relationship between room fire intensity (temperature) and flammability data for materials, ASTM E–84 flame ratings and energy release rate from calorimertry devices is presented for fire spread on lings. The results of the analysis show the significance of two modes of flame spread—wind-aided and opposed-flow spread. The factors important in these spread modes are considered from approximate solutions developed for turbulent flow. As the importance of energy release rate to flame spread in the tunnel test (E–84) and in upward or wind-aided spread is illustrated. The results suggest a possible reason why the ASTM E–84 and in upward or wind-aided spread is illustrated. The results suggest a possible reason why the ASTM E–84 ratings may not be applicable to the performance of low-density combustible linings in wall fires. In the analyses, flame radiation has not been considered. Also the interpretation of energy release rate data for difference scale and orientation effects has been ignored. These two factors must ultimately be addressed.
 
Article
Cone calorimeter analysis was conducted on 18 thermoplastics with different UL-94 vertical burn test (V) ratings. Ratings varied from V-0 to no rating (NR), and the types of thermoplastics included were polycarbonate (PC), acrylonitrile–butadiene–styrene (ABS), PC/ABS blends, high-impact polystyrene (HIPS), polypropylene (PP), and poly(vinyl chloride) (PVC). Our analysis of the cone calorimeter data found that there were correlations between UL-94 V rating and some cone calorimeter measurements (peak heat release rate (HRR) average and HRR at 60 s) and no relationship for other measurements (time to ignition and total heat release). However, no precise correlation was found due to significant differences in flame retardant mechanism and polymer fuel energy values. In this paper, we seek to explain further why a broad quantitative relationship between UL-94 V and cone calorimeter remains elusive, and also to show how the cone calorimeter can be used to understand why a material passes or fails a particular UL-94 V rating. Copyright © 2006 John Wiley & Sons, Ltd.
 
Article
The ISO room corner test is used for classification of surface materials in a number of countries, and as the reference scenario test for the new European single burning item test, its importance increases even more. Time to flashover may be regarded the most important result from the room corner test. In this paper we describe three different calculation models for predicting in which period of testing time flashover in the room corner test will occur. The predictions are all based on test results from the cone calorimeter. The models are a modified version of the Wickström/Göransson model, the model by Östman/Tsantaridis and a model based on multivariate statistical analysis. The three models were applied to a data set containing test results from 57 different products. We found that the modified Wickström/Göransson model and the statistical model generally calculated time to flashover with high precision. The Östman/Tsantaridis model was excellent in prediction of time to flashover within 10 min of testing time, but performed poorer for time to flashover above 10 min. Based on these analyses, a simple, but efficient method for predicting the interval of time when flashover occurs is suggested. Copyright © 2002 John Wiley & Sons, Ltd.
 
Article
Curtain materials are commonly used as decoration, shade, or screen. They are flammable and are usually across a large part of a room, leading to the risk of a high fire hazard. Once ignited, the upward fire spread would accelerate the fire development in an enclosure. In this paper, fire hazard of three typical curtain materials with different pleat rates were tested in an ISO 9705 fire test room. Fire parameters such as temperature field, flame spread rate, heat release rate (HRR), and emitted gases, and the influences of pleat rate and cotton content on flame spread rate were investigated. The correlation between flame spread rate and HRR was discussed. The results show that the upward flame spread has an accelerating rate, and an inverted-triangle burning area would emerge during the combustion. Some horizontal fibrillar structures appear in this burning area. Pleat rate and cotton content have considerable influence on the curtain fire behavior. The flame spread rate shows a linear response to HRR at the early stage. In addition, a function between average flame spread rate and pleat rate for engineering estimation is proposed, and a linear relationship between HRR/mCO and m/mCO has been obtained. The study results provide valuable reference to building fire simulation and safety design. Copyright © 2011 John Wiley & Sons, Ltd.
 
Article
A new experimental method for studying the ablation, ignition and extinction of polymers exposed to flames and other ignition sources is presented. The technique is called the ‘Moving Wire Technique’. The polymer sample is carried on a wire support which is moved uniformity through the ignition source which is a flame in the example given. In the laboratory coordinate system, points along the path of the wire correspond to increasing residence time. The polymer combustion thus becomes a steady-state phenomena which can be studied at leisure with the improvements in precision associated with long time steady-state measurements. In addition to steady-state combustion, ignition and extinction transitions are observed whose onsets are sharp and can be accurately characterized in this system. In a favorable case, a reproducibility of a few parts per thousand is attained in determining critical ignition exposure times and extinction velocities. Results from initial studies of commercial Teflon® and poly-(vinylchloride) are presented. Measurements include critical ignition times and extinction velocities a function of free oxygen concentration. For poly-(vinylchloride), measurements are given of gas phase composition, mass loss of the polymer, and surface temperature of the polymer as a function of exposure time. A discussion is given of the relation of the results to other experiments and potential uses of the technique.
 
Article
A series of literature reviews was undertaken by the National Bureau of Standards to examine the toxicity and chemistry of the effluents produced when seven plastics were decomposed under various thermal and atmospheric condition. These plastics are: acrylonitrile–butadiene–styrenes, nylons, polyesters, polyethylenes, polystyrenes, poly(vinyl chlorides) and rigid polyurethane foams. The English-language literature on each of these was reviewed and published as a separate report of the National Bureau of Standards. Over 400 different thermal decomposition products, many common to more than one plastic, were identified. The toxicity of most of these individual products is products, many common to more than one plastic, were identified. The toxicity of most of these individual products is unknown and an assessment of the toxicity of the multitude of possible combinations is not feasible at this time. Therefore a variety of bioassay toxicity protocols have been used to assess the toxicity of the gaseous atmospheres generated by the thermal decomposition of these plastics. In general, these seven plastics did not produce unusually or extremely toxic pyrolysis or combustion products when compared with those of other synthetic or natural materials. In a few cases involving additives, toxic products of concern were produced.
 
Article
A novel flame retardant (DVN) containing silicon, phosphorus, and nitrogen has been synthesized from the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), vinylmethyldimethoxy silane (VMDMS) and N-β-(aminoethyl)-γ-aminopropyle methyl dimethoxy silane (NMDMS), then incorporated into polycarbonate/acrylonitrile butadiene styrene (PC/ABS) alloy. The flame retardancy of PC/ABS/DVN is evaluated by cone calorimeter and limited oxygen index (LOI) and the thermal degradation behavior is investigated by thermogravimetric analysis under nitrogen and air. The PC/ABS/DVN sample was thermally degraded at 400°C for different amounts of time and studied by Fourier transform infrared spectroscopy to better understand the mechanism of flame retardancy. The results show that the thermal stability and flame retardancy of PC/ABS are improved by incorporation of DVN. Scanning electric microscopy results show that the outer surface of the char layer of PC/ABS/DVN after the LOI test is smooth and the internal structure is like swollen cells, which benefits the flame retardancy of PC/ABS. Copyright © 2007 John Wiley & Sons, Ltd.
 
Article
A review of literature was undertaken to ascertain the current knowledge of the nature of the thermal decomposition products generated from ABS and the toxicity of these evolved products in toto. The literature review encompasses English language publications available through June 1984. This literature surveyed showed that the principal ABS thermooxidative degradation products of toxicologic importance are carbon monoxide and hydrogen cyanide. The experimental generation of these and other volatile products is principally dependent upon the combustion conditions and the formulation of the plastic. The toxicity of ABS thermal degradation products has been evaluated by fire methods. The LC50 (30 min exposure + 14 day post-exposure period) values for flaming combustion ranged from 15.0 mgl−1 to 28.5 mgl−1. In the non-flaming mode of combustion, the LC50 values ranged from 19.3 Mgl−1 to 64.0 mgl−1. Therefore, no apparent toxicological difference exists between the flaming mode and the non-flaming mode. The toxicity of ABS degradation products was found to be comparable with the toxicity of the thermal decomposition products of other common polymeric materials.
 
Article
Four wire coating materials (two of them based on PVC and the two others based on XLPE) were assessed for the irritancy of their smoke, under non-flaming conditions, by using the respiratory depression method, expressed as the RD50. The DIN 53 436 combustion tube was used as the fire model, at a temperature of 550°C (smouldering mode), and the animal model was the mouse. Animals were exposed for 10 min, at concentrations too low to cause lethality. It was found that there was relatively little difference between the irritancy of all four smokes. This was an unexpected result, since it had been predicted that PVC smoke would be much more irritating than XLPE smoke. In fact, the smoke from the PVC compounds had an RD50 roughly in the range of 100-1000 ppm, while the smoke from the XLPE compounds had an RD50 roughly in the range of 10-100 ppm. This means that PVC smoke is somewhat less irritating than XLPE smoke. The components in the smoke of all materials were determined by a combination of continuous gas analysis, ion chromatography and gas chromatography/mass spectrometry, with the objective of understanding the factors causing the irritancy. Hydrogen chloride, one of the major decomposition products of PVC, is also the most important smoke constituent causing irritancy of the smoke. Its irritancy, however, was insufficient, by a considerable margin, to explain the full degree of irritancy found. The RD50 of HCl is, like that of PVC smoke, in the range of 100-1000 ppm. On the other hand, the only compound found in the smoke of XLPE compounds with an RD50 in the same 10-100 ppm range as he overall smoke is methylvinyl ketone. Literature data indicate that polyethylene smoke is rich in long-lived free radicals and that PVC smoke does not contain them. Thus, it is speculated that such free radicals could be the cause of the high irritancy of the smoke from the XLPE wire coating materials.
 
Article
An empirical relation has been developed which correlates and predicts the fire-suppression effectiveness of a wide variety of gaseous, liquid and solid agents. The flame-extinguishment model is based on the premise that extinction is dominated by heat-absorption processes and that a flame is extinguished when sufficient heat has been removed by the extinguishant to reduce the temperature to a limit value. This limit value. This limit is the minimum temperature at which the effective rate of the combustion reactions is sufficient to maintain flamepropagation, and it depends in a predictable way on the properties of the suppressant and flame system. The heat-balance equation describing this is derived in two stages. In the first, a preliminary equation is obtained by considering only those substances which are thermally stable and act only as heat-capacity sinks. In the second, the equation is generalized by consideration of all endothermic reaction sinks, e.g. vaporization, dissociation and decomposition. The general equation correlates most of the extinction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat-extraction data found in the literature. The results suggest that for most substances the extinguishing capacity is related to heat-extraction and that many of the effects previously attributed to chemical mechanisms may be thermodynamic in nature rather than kinetic.
 
Article
The spectral absorptivity of 62 products has been measured in the wavelength region of 0.3–20 µm. Effective absorptivity for fire-induced heat radiation typically lies in the range of 0.75–0.95. It was found that the effective absorptivity varies significantly with the temperature of the heat source. This has implications on the heating of a surface. The effect is more important when the absorptivity is used as input for calculations of ignition temperature and thermal inertia. It was also found that the absorptivity of radiation from fires for products exposed to irradiation in many cases decreased with increased exposure time. This is surprising since, for example, wood that is darkened when exposed to heat obviously has a higher absorptivity in the visual part of the spectrum than fresh non-darkened wood. The reason that was identified for this is because the absorptivity in the IR drops, and measurement results are given which clearly illustrate this. Copyright © 2010 John Wiley & Sons, Ltd.
 
Article
The chemical mechanisms for the action of flame retardants are often mentioned in the literature but the physical modes of action are seldom. Discussed. This article presents one way to quantify their efficiency. The technique is based on literature data for the physical and thermal properties of flams retardants for temperatures from 25°C up to 1000°C. The prolongation of the time to ignition by heat absorption by the retardant and the amount of inert gas evolved by the retardant are calculated at a given radiation for a material flame-proofed with a given amount of the flame retardant. The ability to form an insulating surface layer is considered but not quantified. It is assumed that a medium density wood fibre building boards is treated with 2 kg of flame retardant per m2. The flame retardants included are borates, boric acid, phosphates and silicates. The board is assumed to be irradiated with an intensity of 15 k W m−2. Under these conditions an untreated board ignites after 6–7 min. The time to ignition is prolonged by 1–5 min through heat absorption by the different retardants, and the amount of inert gases evolved may be as high as 2.6 m3 per m2 board. The formation of an insulating surface layer is more difficult to quantify. The results confirm the importance of the physical modes of action of flame retardants and the technique could form the basis for evaluating materials in simulated fire situations.
 
Article
The fire performance of two electric cables (building wires) designed for indoor use has been tested, both as new products and after accelerated thermooxidative ageing. The cables were aged for a maximum time of 16.5 weeks at 80°C. The cables are commercially available, and were constructed using a PVC material in one case and a non-halogenated polyolefin-based material, called Casico, in the other. The effects of ageing on the fire performance of the cables, and the chemical changes that have caused the observed fire behaviour, have been investigated and are discussed. Special attention is paid to the behaviour of the plasticizers that are used in the PVC cable, and how the fire behaviour is affected by the loss of plasticizers from the cable and by the migration of plasticizers between the parts of the cable (insulation, bedding and sheathing). Copyright © 2007 John Wiley & Sons, Ltd.
 
Article
This paper demonstrates the successful use of an infrared pyrometer, operating in the 8–10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non-combustible boards. A small-diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison. The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright
 
Article
In this report we outline recent work on the evaluation of magnesium carbonate-based flame retardants for polymers commonly used in halogen-free flame retardant wire and cable applications: poly(ethylene-co-vinyl acetate) (EVA) and poly(ethylene-co-ethyl acrylate) (EEA). Natural magnesium carbonate (magnesite), synthetic magnesium carbonate (hydromagnesite), and hydromagnesite/huntite blends were combined with EVA or EEA and tested for flame retardancy effectiveness with the cone calorimeter. The flammability results showed that the effectiveness of these carbonates was polymer dependent, suggesting that polymer degradation chemistry played a role in the flammability reduction mechanism. Hydromagnesites were, in general, more effective in reducing flammability, being comparable in performance to magnesium hydroxide. Finally, we report some polymer–clay (organically treated montmorillonite and magadiite) + magnesium carbonate flame retardant results which showed that the nanocomposite yielded mixed results. Specifically, the polymer–clay nanocomposite samples did not always yield the greatest reductions in peak heat release rate. Copyright © 2007 John Wiley & Sons, Ltd.
 
Article
A novel flame retardant (SPDH) containing phosphorus was synthesized through the reaction of 10-(2, 5-dihydroxyphenyl)-9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO-HQ) and synthesized intermediate product 3, 9-dichloro-2, 4, 8, 10-tetraoxa-3, 9-diphosphaspiro(5.5)undecane-3, 9-dioxide (SPDPC). The structure and properties of SPDPC and SPDH were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy and thermogravimetric analysis (TGA). After blending with poly(ethylene-co-vinyl acetate) (EVA), the flame-retardant properties of EVA/SPDH composites were estimated by cone calorimeter, limited oxygen index (LOI) and UL-94 tests, whereas the thermal stabilities were investigated using TGA. The morphological microstructure of the char formed by EVA/SPDH composite after combustion in cone calorimeter was investigated by scanning electron microscopy (SEM). The results indicate that the flame retardant and thermal stability were improved by incorporation of SPDH. The rich foamy char layers were observed from the residues after combustion in a cone calorimeter, which exactly benefits the improvement of thermal stability and flame retardant property of materials. Copyright © 2010 John Wiley & Sons, Ltd.
 
Article
Previous work on the emission of smoke and fumes from overheated aircraft interior materials has included simple monitoring of acids and alkalies by means of a glass electrode in a water-bubbler. In order to put these measurements on a quantitative basis and as part of an attempt to assess the significance of acidic or alkaline fumes in terms of irritant effects, a two-way pH-stat automatic titration apparatus is now used. A small sample of material is heated at a controlled rate to 500°C in a stream of flowing air. The effluent is bubbled through water and automatically titrated for acids or alkalies. The temperatures at which these emissions occur and their amounts can be measured. Good recoveries of acids, alkalies and of both evolved consecutively have been achieved. To assess the utility of the apparatus for actual materials, the acid evolved from various types of PVC was compared. The emissions from three different nylons and from a composite cable were also investigated. Reference materials with various known additives are now being examined by the method and comparisons with irritancy measurements are being made. Ion-chromatography will be used to study the individual acid evolved.
 
Article
This paper presents a closed-form solution with empirical adjustments to predict the time–temperature profile across a lumber section when the exposure history of its surface is known. The formulation is based on the two-dimensional heat-conduction equation that includes the effects of moisture evaporation and pyrolysis of wood. The kinetic constants and adjustment factors needed in the model were estimated from the temperature profile test data of dimension lumber and other published sources. This technique offers a simple practical means to estimate the internal temperatures of structural lumber exposed to high temperatures, and has been effectively implemented in the analyses of protected wood assemblies exposed to fire situations.
 
Article
In this paper the flame-retardant mechanisms of a flame-retardant system consisting of ethylene-acrylate copolymer, chalk and silicone elastomer are linked to its foaming process and to its formation of a final intumescent structure. Thermocouples were placed inside and at the surface of cone calorimeter test specimens in order to measure the temperature at different depths during the formation of the intumescent structure. The temperature and visual observations of the foaming process were then linked to chemical reactions seen with thermogravimetric analysis and also coupled with earlier knowledge of the flame-retardant mechanism. A correlation is seen between the chemical reactions, the temperature (inside and at the surface of a cone calorimeter test specimen) as measured by thermocouples and visual observations in the intumescent process. Further, the outcome of this study provides useful information for achieving a deeper understanding of the flame-retardant mechanisms of the ethylene-acrylate copolymer, chalk and silicone elastomer system. Copyright
 
Article
The synergistic action of antimony (Sb) with bromine (Br) was studied for polypropylene-2,3-dibromopropylpentabromophenyl ether–Sb2O3 systems at various Sb/Br molar ratios. Oxygen index, weight loss rate and heating value were used to evaluate the retardant effect. Bromine and antimony emission and their material balances were measured by gravimetric and X-ray fluorometric analysis of heated samples at each reaction time. Retarded HBr formation in the gaseous phase through SbBr3, SbOBr and Sb4O5Br2 was proved by X-ray diffraction analysis of heated residues and model products. SbBr3 and HBr formation were greatest at Sb/Br ratios of 1/3 and 1/4, respectively, while the highest oxygen index and the lowest weight loss rate and heating value were obtained at 1/4. Consequently, HBr will most probably produce the retardant effect rather than SbBr3. Effective synergistic action at the Sb/Br ratio of 1/4 is explained by presuming the formation of an acidic HBr.SbBr3 complex in the molten phase for the particular reaction pattern of bromine in 2,3-dibromopropylpentabromophenyl either.
 
Article
Partial substitution of ammonium polyphosphate (APP) by manganese dioxide (MnO2) in polyamide 6 (PA-6) fire retarded with 20% of APP strongly increases the fire retardant effect. ‘Linear pyrolysis’ experiments, which are modified cone calorimeter tests, show an increase in the amount and an improvement of the shielding properties of the intumescent char formed on the surface of burning polymer. The enhancement of the yield of aliphatic–aromatic char stable to oxidation was observed in thermogravimetry under air. The fire retardant action of an APP/MnO2 mixture in PA-6 is twofold. On the one hand, this additive promotes involvement of the polymer in the charring and, on the other, the formed manganese phosphate glasses improve the thermo-insulating properties of the intumescent char on the surface of burning PA-6.
 
Article
Nanocomposites of polymers with montmorillonite (MMT) yield upon pyrolysis and combustion an MMT-rich surface of the char. The prevalent approach considers this accumulation as due to the gasification of the polymer and subsequent gradual precipitation of the MMT on the surface. According to the present paper, the enrichment in MMT is postulated to be due to a migration or convection of the MMT to the surface driven mainly by the lower surface free energy of the MMT. The role of the surface free energy in the surface structure of polymer blends, especially those involving a silicon-containing component, is discussed. The enrichment occurs above the glass transition temperature and is temperature dependent. XPS evidence for the accumulation of MMT on the surface of a polystyrene/MMT nanocomposite is reviewed. Its dependence on the stability of the nanocomposite structure, and particularly on the stability of the quaternary ammonium compounds that bind the polymer to the MMT, is pointed out. The importance of the surface free energy in the flame retardancy of polymer blends as well as polymer-additive mixtures is discussed. Copyright © 2003 John Wiley & Sons, Ltd.
 
Article
Novel novolac-based char former silicon-containing phenolic resin (SCPR) was synthesized by the reaction of novolac with γ-aminopropyltriethoxysilane in ethanol via a dehydration reaction, and the synthesized SCPR was characterized by Fourier transform infrared (FT-IR) spectra, proton nuclear magnetic resonance (1H NMR) spectroscopy, and thermogravimetric analysis (TGA). Serving as a synergist of magnesium hydroxide (MH) for the flame retardancy of polyamide 6 (PA6), it shows that the introduction of silicon in the structure of novolac molecule can greatly increase the charring performance of phenolic resin, and effectively eliminate the melt drips of PA6, thus improving the flame retardancy of the PA6. Compared with conventional novolac, the thermal oxidative stability of SCPR was obviously enhanced in the presence of MH due to the decrease of phenol hydroxide groups sensitive to oxidation, as well as the high energy Si–O bond introduced in the molecular structure. Copyright © 2010 John Wiley & Sons, Ltd.
 
Article
Comparison of oxygen and nitrous oxide indices indicates that ammonium polyphosphate (APP) should act in the condensed phase when added to nylon 6 (PA-6). A detailed study of the thermal degradation mechanism of PA-6/APP mixtures is carried out. A polyphosphate ester is formed on heating, which is the precursor of an intumescent char. Evidence is given of the thermal insulating action of the intumescent char which slows down the rate of combustion of the polymer.
 
Article
Owing to their low cost phosphorus fire-retardants find vast application in making fire-retardant cellulosic compostions. They have been used both as a physical additive as well as part of the polymer structure. Acid forming phosphorus compounds are generally effective in cotton and other cellulosic. Acidic retardants produce char via a dehydration process and this brings about the final fire-retardancy in phosphate-containing composition. High efficiency of phosphorus fire retardants in polyurethane foam has also been suggested to be the result of stable char formation. The char affects the flammability in the three following ways: reduction of flammable fuel, insulation by the char and coating by the non-volatile thermally stable phosphorous acids which screen the hot carbon from the oxygen. Nitrogen-phosphorus synergism in cellulose in controversial and evidence indicates that it is non existent in polymers.
 
Top-cited authors
B. Schartel
  • Bundesanstalt für Materialforschung und -prüfung
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  • Fire Science and Technology Inc.
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Serge Bourbigot
  • Université de Lille
Richard E. Lyon
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