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Preview: Fire and Materials

Fire and Materials

Wiley Online Library : Fire and Materials

Published: 2017-12-01T00:00:00-05:00


Influence of out-of-plane fiber orientation on reaction-to-fire properties of carbon fiber reinforced polymer matrix composites


This work investigates the influence of the out-of-plane orientation of carbon fibers on the reaction-to-fire characteristics of polymer matrix composites. A deep insight into combustion processes is gained, which is necessary to fully understand and assess advantages of composites with out-of-plane fiber angles. Epoxy-based Hexply 8552/IM7 specimens with primarily low fiber angles between 0° and 15° are characterized by cone calorimetry. Heat release during fire is greatly affected by the out-of-plane fiber angle because of the thermal boundaries created by the fibers. The advancement of the pyrolysis front during fire was determined from peak heat release rates and validated by temperature measurements along the back surface of the panels, representing a novel method of determining position-dependent pyrolysis migration velocity. These measurements show a transverse shift in pyrolysis front velocity for increasing out-of-plane fiber angles. Pyrolysis pathways between the fiber boundaries facilitate faster combustion through the composite thickness, especially for increasing angles from 0° to 15°. It was determined that under the chosen conditions, the pyrolysis front advances approximately 4 times faster when propagating parallel to the fibers than perpendicular.

Effects of opening edge treatment and EPS thickness on EPS external thermal insulation composite systems (ETICS) façade reaction-to-fire performance based on JIS A1310 standard façade fire test method


External thermal insulation composite systems (ETICS) are quite common in constructions. However, the combustible insulation core induces serious fire disasters, especially considering thermoplastic expanded polystyrene (EPS) has been widely used as insulation core. Most of EPS ETICS building fire is caused by window spreading fire. The window opening edge treatment plays an important role in EPS ETICS fire prevention. Presently, in order to investigate optimal opening edge treatment and EPS thickness effects on EPS ETICS reaction-to-fire performance, façade fire tests based on JIS A 1310 standard façade fire test method were carried out by testing a series of EPS ETICS specimens varying EPS thickness, opening edge treatment methods and heating intensity. It is found that back-wrapping is a good opening edge treatment method. When the EPS ETICS specimen is treated by back-wrapping opening edge treatment method, the peak temperature, EPS burn area, time (20 minutes) averaged temperature, and heat flux density become low. The time (20 minutes) averaged temperature of each position from T1 to T5 versus EPS thickness is linear at heating intensity 300 or 600 kW. The averaged ratio of EPS burn area above opening (Sa) and below opening (Sb) is approaching 3.058.

Gypsum board failure model based on cardboard behaviour


This study aims to analyse the importance of gypsum plasterboard cardboard for fire resistance. A new hypothesis considering the failure based on the cardboard degradation is defined. This hypothesis comes from the thermal analysis of gypsum and cardboard performed in the simultaneous thermal analysis apparatus. Simultaneous thermal analysis results also allow defining the dehydration process of the gypsum. A numerical model that considers gypsum dehydration and the failure hypothesis has been developed by using Fire Dynamic Simulator. This numerical model is validated against 6 fire resistance tests. Results show that we can appropriately tune the numerical model (for predicting time to failure) based on the thermal properties of cardboard.

Experimental and numerical study of interactions between sprinklers and natural smoke vents


Real scale experimentations have been conducted in order to investigate interactions that may occur in a compartment where sprinklers and Smoke and Heat Exhaust Vent Systems coexist. Fuel oil spray was used as fire source with steady heat release rate of 400 and 800 kW. Both sprinkler system and natural Smoke and Heat Exhaust Vent Systems were designed according to the French standards. Effect of vent on sprinkler activation time was studied. An analysis of the temperature field inside the compartment was conducted while vent was opened prior or after sprinkler activation. Simulations of the experiments were also carried out with Fire Dynamics Simulator v.6 for validation purpose and also to provide supplementary data regarding soot flow rate and energy extracted at the vent.

Effect of phytic acid–modified layered double hydroxide on flammability and mechanical properties of intumescent flame retardant polypropylene system


Phytic acid–modified layered double hydroxide (Ph-LDH) was synthesized via coprecipitation method and subsequently was used in polypropylene (PP) by combining with an ammonium polyphosphate (APP) via melt compounding method. The synergistic effect between APP and Ph-LDH on the thermal stability, flammability, and mechanical properties of the resultant PP composites was investigated by thermogravimetric analysis, limiting oxygen index, vertical burning test (UL-94), cone calorimeter tests, tensile test, and impact test. Morphologies of the chars obtained from the samples after the cone calorimeter tests were studied by scanning electron microscopy. The combination of APP and Ph-LDH slightly influenced the impact and tensile properties of PP. Also, the synergistic effect between APP and Ph-LDH occurred in the cone calorimeter test. Moreover, the combination of APP and Ph-LDH produced better quality char that effectively suppressed the spread of the flame and volatile and finally extinguished the fire.

Temperature distribution of the straight bar, fixed into a heated plane surface


The authors present the first stage of their theoretical and experimental investigations focused on the fire protection of the steel structures using intumescent paint. In this initial stage, their results concerning the temperature distribution law (the theoretical law is validated by effective meticulously conducted measurements) are described. Their original testing bench destined to perform high-accuracy monitoring of the temperature distribution along straight bars, having a given αg angular positioning with respect to the vertical direction is also described. By involving this testing bench in meticulously conducted experiments, the authors obtained both the effective temperature distribution along the bars and also validated the theoretical (exponential) thermal distribution law. By searching experiments, they also validate the m = const. hypothesis with respect to the massive cross-sectional bars. Among their further goals, one can mention the searching experimental analysis on the validity of the m = const. hypothesis for the tubular cross-sectional bars, followed by a combined experimental and numerical analysis of the 2-D and 3-D (unprotected and protected with intumescent paint layer) structures, as well as the paint layer's thickness optimisation, too.

Flammability of wood plastic composites prepared from plastic waste


The flammability of wood plastic composites manufactured from recycled plastics was investigated by using the cone calorimetry technique. The peak of the heat release rate was 12% to 25% lower compared to references produced from pure polyethylene- and polypropylene-based composites. The total heat capacity and mass loss rate were also smaller for recycled material compared to the references. The stability of the composites was improved due to the presence of various thermally stable compounds, eg, traces of fire retardants, pigments, and other additives and impurities that can be present in recycled material. Incorporation of carbon black into the secondary materials did not reduce the peak of the heat release rate, but the total heat capacity and mass loss rate decreased further.

Surface sedimentation and adherence of Nano-SiO2 to improve thermal stability and flame resistance of melamine-formaldehyde foam via sol-gel method


Melamine-formaldehyde foam possesses intrinsic flame retardance; however, relative poor thermal stability and a certain amount of heat release rate restrict its applications in heated environment to a degree. In the present research, sol-gel method has been adopted to precipitate nano-SiO2 particles on the surface of the melamine-formaldehyde foam's fibers to construct a protective inorganic gel layer. Taking advantages of the shielding effects of the gel layer, the thermal-oxygen degradation of the foam can be greatly retarded during heating; hence, the thermal stability is remarkably improved, and the flame retardance is further enhanced. In addition, introducing a small amount of membrane-forming agent in the sol-gel system can make the depositional nano-SiO2 particles well adhered to avoid dusting.

The intumescent flame-retardant biocomposites of poly(lactic acid) containing surface-coated ammonium polyphosphate and distiller's dried grains with solubles (DDGS)


This work aims to develop the poly(lactic acid) (PLA) biocomposites with high flame-retardant performance, which can be applied in electronic and electrical devices as well as automotive parts. First, an intumescent flame retardant composed of ammonium polyphosphate (APP) as the acid source and the blowing agent, and the distiller's dried grains with solubles (DDGS) as the natural charring agent was designed. The surfaces of DDGS and APP were coated by degradable polymeric flame-retardant resorcinol di(phenyl phosphate) (RDP), and the coating effects were analyzed. And then the flame-retardant biocomposites of PLA with RDP-coated DDGS (C-DDGS) and RDP-coated APP (C-APP) were prepared. The limited oxygen index value of the biocomposites with loading of 15 wt% C-DDGS and 15 wt% C-APP reached 32.0%, and UL-94 V-0 was attained. The biocomposites also had good mechanical properties and the tensile strength of this sample reached about 57 MPa. Finally, the char residues after burning were analyzed and the flame-retardant mechanism was discussed.

On a planar thermal analysis of intumescent coatings


The paper discusses a complex model for a nonstationary planar thermal analysis of expandable intumescent coatings. Following the existing one-dimensional models, we develop novel and improved equations for the two-dimensional thermal analysis of intumescent coatings. A progressive expansion due to chemical reactions, phase changes, and the time and temperature-dependent thermal properties of the coating are considered. In the heating process, the coating may locally experience virgin, intumesced, or charred phases, and their transition with time. The rate of the density loss due to the pyrolysis reaction is described with the Arrhenius equation. The thickness of the coating is assumed to increase enormously during the pyrolysis. Consequently, the energy and mass equilibrium equations are formulated with respect to both the deformed and undeformed configuration. Since most of material properties of commercial products are not given by manufacturers, an innovative procedure is proposed to determine the time-dependent thermal conductivities and remaining fundamental properties of the coating from the set of measured temperatures. This, together with the two-dimensional formulation of the thermal equations with respect to the undeformed configuration, makes the present model unique and appropriate for the thermal analyses of an arbitrary steel cross section protected with intumescent coatings.

Fire performance of brominated and halogen-free flame retardants in glass-fiber reinforced poly(butylene terephthalate)


This paper investigates the effects of brominated and halogen-free fire retardants on the fire performance of glass-fiber (GF) reinforced poly(butylene terephthalate) (PBT). Brominated polystyrene was used as the brominated fire retardant, whereas aluminum diethylphosphinate with/without nanoclay as halogen-free fire retardants (HFFRs). Tests were conducted by using thermogravimetric analysis, limiting oxygen index (LOI), UL94, and the cone calorimeter. Thermogravimetric analysis results show that decomposition of GF plus PBT (PBT + GF) starts earlier in the presence of all fire retardants (FRs). In the cone calorimeter, all FRs reduce significantly the heat release rate (HRR) compared with PBT + GF, with brominated polystyrene achieving lowest HRR primarily because bromine released in the pyrolysis gases inhibits combustion. Brominate polystyrene does not, however, affect the mass loss rate. Aluminum diethylphosphinate alone has significant effects on reduction of both HRR and mass loss rate, which become considerably more when combined with nanoclay. It was also found that the combustion efficiency of the brominated polystyrene compound is much lower than that of HFFRs, indicating that brominated polystyrene has higher gas phase flame retardant efficiency compared with HFFRs because the bromine radicals released during degradation of brominated polystyrene effectively quench the chemical reactions of the pyrolysis gases due to degradation of PBT.

The ammonium nitrate explosion at West, Texas: A disaster that could have been avoided


On April 17, 2013, an explosion of ammonium nitrate (AN) fertilizer stored at the West Fertilizer Company resulted in 15 deaths, 260 injuries, and the destruction of a sizable portion of the town. AN fertilizer is classified as an oxidizer, not as an explosive; nonetheless, it is a chemical which can detonate, and there is a century's worth of history of such explosions, some of them in manufacturing operations, but many in storage or transport. A review of incidents showed that 100% of AN fertilizer explosions in storage or transport had a single cause—an uncontrolled fire. Thus, AN fertilizer explosions in storage are preventable accidents, because technology to preclude uncontrollable fires also has been available for a century. In the case of transport accidents, uncontrolled fires may not be avoidable. However, technologies exist that can make AN less likely to explode, and to show greatly reduced explosion intensity, if driven to explosion. None of these safety measures were in place for this disaster. Details of necessary fire safety measures and the effectiveness and utility of existing regulations for AN are examined. This is important because most AN storage facilities in the United States are similarly inadequate in their fire safety.

Experimental research on the burning behavior of dragon juniper tree


Tree crown fire is one of the extreme fire behaviors in the wildland-urban interface. This paper presents an experimental study on the burning behaviors of single and triple dragon juniper trees. The mass loss, flame height, plume temperature, radiation, and fire interaction are measured. It is found that the foliage moisture content and flame mergence dominate the mass consumed percentage (defined as the ratio of the total mass loss to initially total mass), while the tree crown height and flame mergence determine the flame height. The peak mass loss rate is mainly affected by the moisture content and tree species. For triple tree fires, the peak mass loss rate is also affected by the spacing due to the coupled effects of heat feedback enhancement and air entrainment restriction. Results also show that the flame height significantly increases as the spacing decreases. The spacing holds a significant effect on the fire plume temperature distribution and thermal radiation field. Empirical correlations are also developed for the flame height, radial temperature, and radiant heat flux distribution based on physical interpretation of the tree burning behaviors.

Oxidation behavior of carbon steel in simulated kerosene combustion atmosphere: A valuable tool for fire investigations


Fire investigations aim to establish the origin and cause of fires by collecting and analyzing the comprehensive fire-related evidences. Metallic materials exposed to the fire scene environments are usually subjected to melting and/or high-temperature oxidation, and they have been considered vital parameters for temperature determination, as recommended in NFPA 921. The oxide characteristics obtained from the conventional fire investigations primarily rely on simple visual observations such as the variations in oxide color, the so-called “oxidation patterns.” However, such information is not sufficiently convincing due to the complex nature of oxides formed in the fire scene. The oxide color is strongly affected by the type of oxide, the oxide thickness, the concentration of contaminant, and the interactions among different oxides. In this study, Q235 structural steel samples have been exposed to high-temperature air and simulated kerosene combustion conditions at certain temperatures and for indicated periods. The oxidation rate was examined by thermogravimetric analysis. The morphologies and microstructures of the oxide scales were investigated by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffractions. The results show that the oxide properties are strongly dependent on the oxidation temperature and oxidation atmospheres. These oxidation behaviors are expected to provide useful information on identifying fire characteristics.

The effect of the trimerization catalyst on the thermal stability and the fire performance of the polyisocyanurate-polyurethane foam


In this work, 3 currently used trimerization catalysts, TMR-2 (quaternary ammonium), K-15 (potassium octoate), and PU-1792 (potassium acetate) were used to produce rigid polyisocyanurate (PIR) foams with certain amounts of isocyanurate contents. The results from Fourier transform infrared (FTIR) quantitative analysis showed that PU-1792 had the highest catalytic efficiency in isocyanurate formation. Then, the effect of different amounts of PU-1792 catalyst on isocyanurate ring output was further investigated, and the result showed that the highest amount of isocyanurate ring formation could be attained by the 5 pphp of PU-1792 catalyst. It was also found that the increased amount of isocyanurate ring could result in reduced cell size, improved compressive strength, and lowered thermal conductivity of PIR foam. The results from thermogravimetric analysis (TGA) and cone calorimeter (CONE) test revealed that the thermal stability and fire performance of PIR foam could be improved with the increased amount of isocyanurate ring. Furthermore, the CONE test indicated that the smoke production of PIR foam decreased approximately 51.7% in comparison to the reference polyurethane (PU) foam, and the SEM image of char morphology showed that the char of PIR foam was more compact than PU foam.

Synthesis of microencapsulated zinc stannate and its application in flame-retardant poly(vinyl chloride) membrane material


The novel core-shell magnesium dihydroxide (MDH)/zinc stannate (ZS) and melamine-formaldehyde (MF) resin/MDH/ZS microcapsules were prepared. Their structures were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and X-ray photoelectron spectroscopy analysis techniques, then its flame-retardant application in poly(vinyl chloride) (PVC) composites. The PVC composites were investigated by the limited oxygen index, smoke density, vertical burning test (UL-94), cone calorimeter test, scanning electron microscopy, and thermogravimetric analysis. When directly exposed to flame, PVC generated a high-density char layer, giving PVC a self-extinguishing property. Furthermore, when the mass ratio of MDH/ZS and MF/MDH/ZS microcapsules were 2/8 and 10/2/8 with 16 wt% loading, the results showed that the limited oxygen index value reached 29% and 33%, and the smoke density value reached 51% and 41%. Thus, the microencapsulated ZS could greatly suppress the generation of the flame and smoke during combustion, showing potential applications as multifunctional advanced composites. Two aspects of this manuscript will make it interesting to general readers of Fire and Materials. The magnesium dihydroxide (MDH)/zinc stannate (ZS) microcapsule was firstly prepared via chemical deposition method, and then melamine-formaldehyde (MF) resin/MDH/ZS microcapsule was secondly prepared. The smoke density of poly(vinyl chloride) (PVC)/MDH/ZS microcapsule and PVC/MF/MDH/ZS microcapsule composites were less than half of the neat PVC. With the addition of the 16 wt% of MDH/ZS or MF/MDH/ZS microcapsules into PVC, the limited oxygen index value of PVC composites achieved a significantly high limited oxygen index value at 29%, 33%, and the smoke density value of PVC reached 51%, 41%, respectively. They are V-0 rating in UL-94 test. The results indicated that MDH/ZS and MF/MDH/ZS microcapsules behaved as an environmental friendly flame retardant and smoke suppressant. Thus, this study demonstrated the great potentials of the intrinsically flame-retardant MDH/ZS and MF/MDH/ZS microcapsules in the application of high performance matrix resin and composite material.

Development of water content sensor composed of small copper electrodes for use during fire resistance tests of concrete and cement mortar elements


The purpose of this study is to develop a sensor for measuring the water content in concrete and cement mortar elements usable in fire tests. Annealed copper wires were used as electrodes of the water content sensor. Each electrode is 20 mm in length and 0.8 mm in diameter. The separation distance between the electrodes is 2 mm. By measuring the electric resistance, water content can be monitored continuously. Mortar bar specimens were used to calibrate the sensor by measuring electric resistance as a function of water content at a constant temperature of 26°C. The temperature dependence of the electrical resistance was approximated by a functional relationship developed by Ichinose for a similar type of sensor. As a result, a calibration formula was derived for electrical resistances in the range of 1.51 to 2330 kΩ, temperatures in the range of 10 to 175°C, and volumetric water content in the range of 0.084 to 0.201 m3/m3. To verify the applicability, the sensors were embedded in a wall specimen heated by ISO 834 fire for 30 minutes. As a result, it was possible to measure the water contents continuously.

Thermal and residual mechanical profile of recycled aggregate concrete prepared with carbonated concrete aggregates after exposure to elevated temperatures


Thermal and residual mechanical performance of recycled aggregate concrete (RAC) prepared with recycled concrete aggregates (RCAs) after exposure to high temperatures has so far received less attention than that of conventional concrete prepared with natural aggregates (NAs). This study experimentally investigated thermal and residual mechanical performance of RAC prepared with different replacement percentages of non-carbonated and carbonated RCAs after exposure to high temperatures. The residual mechanical properties, including compressive strength, modulus of elasticity, and peak strain at the maximum strength, were measured for evaluating the fire resistance of RAC. The experimental results showed that although the fire-resistant ability of natural granite aggregates was high, thermal deterioration of the conventional concrete after exposure to 600°C, presented by thermal induced mesocracks, was more serious than that of RAC due to thermal incompatibility between NAs and mortar. Using the carbonated RCAs can reduce the width of thermal mesocrack in RAC. The residual mechanical properties of RAC after exposure to 600°C can be obviously improved by incorporating 20% to 40% of the carbonated RCAs. For the RAC made with the 100% carbonated RCAs, the ratio of residual to initial compressive strength after exposure to above 500°C was even higher than that of the conventional concrete.

An experimental setup for observation of smoldering-to-flaming transition on flexible foam/fabric assemblies


Fires that involve upholstered furniture frequently begin as a smoldering combustion and, with time, transition to a flaming combustion, which sharply increases the level of hazard. Therefore, understanding how the compositions of the primary flammable components of the furniture, ie, flexible foam and upholstery fabric, affect this transition is important for fire safety considerations. In the current study, an experiment was designed to observe this transition using a sample consisting of 30 × 15 × 6 cm3 rectangular foam block covered with 30 × 15 cm2 piece of fabric. For a representative system of 1.8 lb/ft3 (29 kg/m3) flexible polyurethane foam and 11 oz (0.37 kg/m2) cotton fabric, 0.69 transition probability was measured. This probability decreased by a factor of 4 when a small amount of phosphorus-based flame retardant, Fyrol® HF-9, was added to the foam. The transition to flaming was speculated to be associated with the formation of adjacent pyrolysis and smoldering regions within the foam. The pyrolysis region, dominated by anaerobic decomposition, provided gaseous fuel, the ignition of which resulted in the transition. The smoldering region, dominated by oxidation reactions at the solid-gas interface, generated the heat necessary to maintain the pyrolysis process and ignite the gaseous fuel.

Flexible transparent flame-retardant membrane based on a novel UV-curable phosphorus-containing acrylate


A novel phosphorus-containing acrylate monomer (AOPA) was synthesized starting from 2-methy-2,5-dioxo-1,2-oxaphospholane and hydroxyethyl acrylate. The structure of AOPA was characterized with FTIR and 1H NMR. AOPA shows good compatibility with polyethylene glycol diacrylate (PEGDA) and can polymerize with PEGDA under UV light irradiation at different mass ratios to form membranes with high transparency (above 88.9% of light transmittance in the range of 400-800 nm) and flexibility. Incorporating 20 wt% of AOPA in PEGDA reduced the total heat release and peak rate by 50.3% and 38.4%, respectively, as measured by micro combustion calorimeter. The membrane containing 40 wt% of AOPA with 0.4 mm thickness can pass the UL94 V0 rating, and limiting oxygen index reaches 33.4%. TG-FTIR and SEM-EDX analysis show that the presence of AOPA depresses the thermal degradation and promotes the char formation.

Study of the relationship between thermal insulation behavior and microstructure of a fire-resistant gel containing silica during heating


Adding a transparent gel containing silica between 2 sheets of glass could improve the fire resistance of laminated glazing by its thermal intumescent behavior at high temperature. In this study, a custom fire test shows that the glazing reaches the highest thermal insulation rating of 40 minutes when the molar ratio of SiO2 and Na2O in the gel is 4.0, but above this ratio, the thermal insulation rating of the glazing decreases with the increasing silica content. Thermal and scanning electron microscopic analyses have been used to investigate the thermal behavior and microstructure of the residual layer, respectively. The results indicate that, although the high silica content is responsible for the high amount of residue that is essential in the formation of a protection barrier between fire-exposed and unexposed sides of the glass, it is not the only factor that resulted in the improved thermal insulation of the glazing.

Specimens size, aggregate size, and aggregate type effect on spalling of concrete in fire


This paper attempted to isolate variables that govern concrete spalling when exposed to a hydrocarbon fire. The influence of specimen size was investigated by studying 4 specimen sizes consisting of cylinders, columns, and panels. Three aggregate sizes, 7 mm, 14 mm, and 20 mm were used in the concrete mixes to determine their effect on concrete spalling. Influence of aggregate type on concrete spalling was also investigated. Forty-two different specimens were considered in this investigation. Concrete spalling was quantified as nominal spalling depth, which has been presented as a new way of quantifying the degree of concrete spalling. The results indicated that specimen size did have an effect on the spalling of concrete under hydrocarbon fire exposure and that nominal spalling depth of concrete increases as the specimen size increases. Aggregate size effect was evident when the maximum aggregate size increased from 7 mm to 20 mm, and explosive spalling was more severe for specimens with small size aggregates. Specimens with 14-mm aggregate size showed inconsistent results and the spalling behavior witnessed was more random and sporadic. The type of aggregate used has no clear bearing on concrete spalling given both aggregates had similar linear expansion profiles.

Experimental studies on the thickness of upward flame over poly(methyl methacrylate) slabs


Experiments were performed to investigate the flame thickness of the upward flame on the poly(methyl methacrylate) slabs with width of 100-400 mm. The results indicated that the flame thickness exhibited an increase first and then decrease trend in the upright orientation, and the maximum thickness location was approximately equal to the pyrolysis front location. The thickness of the flame along the lateral side of slab was less than that of the interior flame. The flame maximum thickness as a function of pyrolysis height and width was obtained, which showed the maximum thickness provided a power law increase with the pyrolysis height and width. Furthermore, the maximum thickness exhibited a power law increase with the total heat release rate as well. Based on the obtained flame thickness, the radiation heat flux at the pyrolysis height was estimated by using a simplified model. Comparison with the calculated convective heat flux revealed approximated pyrolysis heights for upward flame transition from convective heat flux controlled to radiation heat flux controlled.

Prediction of time to ignition in multiple vehicle fire spread experiments


This paper describes the application of the flux-time product ignition criterion and the point source flame radiation model to predict the time to ignition in multiple vehicle spread scenarios. Ten experiments from the literature have been selected due to sufficiency of information required to apply the methods. The outcome of this work is to be applied to a risk-based model for the design of car parking buildings to determine when and if a fire spreads between vehicles; therefore, the analysis suggests properties of a representative material that can reasonably account for those external vehicle components that are most likely to ignite first. The application of both methods to the complex problem of multiple vehicle ignition requires several assumptions and simplifications which are discussed in the paper.

Cable tray fire tests in a confined and mechanically ventilated facility


Cable fires are one of the main fire hazards in nuclear power plants. As part of the cable fire spreading (CFS) campaign of the OECD PRISME-2 programme, 3 real-scale cable tray fire tests were performed in open atmosphere (1 CFS support test, named CFSS-2) and in a confined and mechanically ventilated facility (2 CFS tests, named CFS-3 and CFS-4). This study aims at investigating the effects of confined and ventilated conditions on cable tray fires that used a halogen-free flame retardant cable-type. The CFS-3 and CFS-4 tests involved 2 ventilation renewal rates of 4 and 15 h−1, respectively. The confined conditions lead to decrease the fire growth rate and the peaks of mass loss rate and heat release rate, compared with open atmosphere. The reductions are larger for the lower ventilation renewal rate. Furthermore, it is shown that the CFS-4 test may be classified as a well-ventilated fire and the CFS-3 test as an under-ventilated fire. For this last one, its fire characteristics and its consequences in the fire room highlight an oscillatory behaviour, with the same low frequency, for about 30 minutes. These oscillations arise from successive combustions of unburnt gases.

Flame retardant treated flax fibre reinforced phenolic composites: Ageing and thermal characteristics


In this study, flax composites were prepared from flax fabric and phenolic resin. Chemical treatments were imparted to the fabric to improve adhesion between the fabric and the phenolic matrix. Diammonium phosphate was applied to improve the flammability of the composites. The thermal and flammability properties of the untreated, chemically treated, and flame retardant (FR) treated flax fabric reinforced phenolic composites were studied. Ageing studies were carried out by subjecting the composites to varying conditions of temperature and humidity in an environmental chamber for 2 weeks. FR treatment of flax fabric was shown to be very effective in improving flame retardancy of the composites due to decreased peak heat release rate (PHRR) and smoke production rate (SPR). Thermogravimetric analysis (TGA) of composites showed that after FR treatment, the decomposition temperatures shifted to lower temperatures. Ageing studies revealed that the mechanical properties of untreated, chemically treated and FR treated composites decreased with an increase in ageing temperature.

New polyether diols as flame retardants for polyurethane: Derivatives of epoxy-functionalized phosphonates and phosphates


Phosphorus-containing epoxides were used to generate several oligomeric polyether diols, which were in turn utilized in the preparation of model polyurethane (PU) samples, either as comonomers in the polymerization (Prep samples) or solvent blended into a priori prepared PU (Blend samples). The resultant samples were evaluated for heat release reduction potential using microcombustion calorimetry. Several variables were investigated in the oligomerization of the original epoxides, such as presence of initiator, epoxide comonomer, and solvent. The oligomer mixtures were thoroughly characterized, using NMR, mass spectrometry (MS), elemental analysis, and viscosity measurements. The final PU Prep samples were carefully analyzed to demonstrate and evaluate the degree of chemical incorporation of the polyether diols into the PU main chain. Results from the heat release studies demonstrated that incorporation of the phosphorus-containing diol did lower flammability, but the structure of the original epoxide, as well as the oligoimerization conditions, had an effect on heat release reduction. The results are complex and require further study, but the phosphonate-based materials showed greater heat release reduction potential, both in the form of Prep and Blend samples, especially in one case of a Blend sample, where a notable amount of intumescent char was formed.

Enhancing egress drills: Preparation and assessment of evacuee performance


This article explores how egress drills—specifically those related to fire incidents—are currently used, their impact on safety levels, and the insights gained from them. It is suggested that neither the merits of egress drills are well understood, nor the impact on egress performance well characterized. In addition, the manner in which they are conducted varies both between and within regulatory jurisdictions. By investigating their strengths and limitations, this article suggests opportunities for their enhancement possibly through the use of other egress models to support and expand upon the benefits provided. It is by no means suggested that drills are not important to evacuation safety—only that their inconsistent use and the interpretation of the results produced may mean we (as researchers, practitioners, regulators, and stakeholders) are not getting the maximum benefit out of this important tool. © 2017 Her Majesty the Queen in Right of Canada. Fire and Materials StartCopText© 2017 John Wiley & Sons, Ltd.

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Revealing the inner secrets of intumescence: Advanced standard time temperature oven (STT Mufu+)—μ-computed tomography approach


Intumescent coatings have been used for fire protection of steel for decades, but there is still a need for improvement and adaptation. The key parameters of such coatings in a fire scenario are thermal insulation, foaming dynamics, and cohesion. The fire resistance tests, large furnaces applying the standard time temperature (STT) curve, demand coated full-scale components or intermediate-scale specimen. The STT Mufu+ (standard time temperature muffle furnace+) approach is presented. It is a recently developed bench-scale testing method to analyze the performance of intumescent coatings. The STT Mufu+ provides vertical testing of specimens with reduced specimen size according to the STT curve. During the experiment, the foaming process is observed with a high-temperature endoscope. Characteristics of this technique like reproducibility and resolution are presented and discussed. The STT Mufu+ test is highly efficient in comparison to common tests because of the reduced sample size. Its potential is extended to a superior research tool by combining it with advanced residue analysis (μ-computed tomography and scanning electron microscopy) and mechanical testing. The benefits of this combination are demonstrated by a case study on 4 intumescent coatings. The evaluation of all collected data is used to create performance-based rankings of the tested coatings.

Development of a screening test based on isothermal calorimetry for determination of self-heating potential of biomass pellets


For the risk for spontaneous combustion in storage of biomass pellets to be assessed, it is important to know how prone the fuel is to self-heating. There are traditional methods that are used to determine self-heating characteristics of fuels, eg, basket heating tests. The results from basket heating tests indirectly give the reactivity from a series of tests at high temperatures. This paper presents a sensitive screening test procedure for biomass pellets using isothermal calorimetry for direct measurement of the heat production rate at typical bulk storage temperatures. This method can be used to directly compare the reactivity of different batches of biomass pellets. The results could be used, eg, by storage security managers to gain better knowledge of their fuels propensity for self-heating and thereby for safer storage. A large number of tests have been performed to develop the test procedure presented. Different parameters, such as temperature, type of the test sample (powder/crushed or pellets), mass of test sample, and preheating time, have been varied. Furthermore, gas concentrations in the sample ampoule have been measured before and after some tests to study the oxygen consumption and the formation of CO and CO2. Three different types of pellets with different characteristics were tested to assess the variation in behaviour. Based on these tests, a screening test procedure is presented with a test temperature of 60°C, a sample size of 4 g, a 15-minute preheating period at the test temperature, and 24-hour test duration.

An exploration of enhancing thermal protective clothing performance by incorporating aerogel and phase change materials


Thermal liners play a critical role in thermal protective performance for firefighter gear. Effective engineering of textile material is necessary to enhance this protective performance. A modified thermal protective erformance (TPP) tester was used to study the influence of incorporating aerogel and microencapsulated phase change materials (MPCMs) in thermal liners (including a traditional thermal liner, phase-change layer, and aerogel layer) and the relevant parameters associated with enhanced thermal liner performance. Two different phase-transition temperature (45°C and 50°C) of MPCM were selected. The samples were exposed to a medium intensity radiation of 15 kW/m2 for 240 seconds, and a skin burn model was applied for second-degree burn prediction. Given the selected, results showed that the best TPP in this study was achieved when the phase-transition temperature of MPCM was 45°C and the layering order consisted of the traditional thermal layer (closest to heat source), followed by an aerogel layer, and a final MPCM layer. The predicted second-degree burn time was 218.3 seconds and increased by 90% compared with only containing traditional thermal liner with a thickness of 5 mm. For all 3 materials contained in the thermal liner, the relationship between absorbed energy and predicted second-degree skin burn time indicated that they had a remarkable negative linear correlation (R2 was 0.9792). The experimental data and predicted results were in good agreement, with a correlation coefficient (R2) of 0.9911. The findings provide a scientific basis for future textile engineering and a novel approach to improve TPP.

Improvement of the flame retardancy of plasticized poly(lactic acid) by means of phosphorus-based flame retardant fillers


The aim of this study is to improve the flame resistance and toughness of poly(lactic acid) (PLA) with the addition of low amount of flame retardant fillers and plasticizer simultaneously. Poly(ethylene glycol) (PEG) was used as plasticizer for PLA. Ammonium polyphosphate, boron phosphate, and tri-phenyl phosphate (TPP) were used as flame retardant additives. Among these flame retardant additives, boron phosphate was synthesized from its raw materials by using microwave heating technique. Characterization of PLA/PEG-based flame retardant composites was performed by conducting tensile, impact, differential scanning calorimeter, thermal gravimetric analysis, scanning electron microscope, limiting oxygen index, and UL-94 vertical burning tests. Mechanical tests showed that the highest tensile strength, impact strength, and elongation at break values were obtained with the addition of ammonium polyphosphate and TPP into PLA/PEG matrix, respectively. Scanning electron microscopy analysis of the composites exhibited that the more homogeneous filler distribution in the matrix was observed for TPP containing composite. The best flame retardancy performance was also provided by TPP when compared with the other flame retardant additives in the plasticized PLA-based composites.

Preparation and studies of new phosphorus-containing diols as potential flame retardants


Several new phosphorus-containing potential flame retardants (FRs) were prepared and evaluated for heat release reduction potential, by incorporation of the molecules into polyurethane samples, generated from methylene diphenyl diisocyanate and 1,3-propane diol. The potential FRs were all prepared from commercial diisocyanates, with the phosphorus-containing substructure introduced as a semicarbazone. All of the target structures were diols, to facilitate their incorporation into a polyurethane main chain. The polyurethane samples were prepared via copolymerization, and analysis clearly demonstrated that the potential FRs were chemically incorporated, prior to heat release testing. The heat-release reduction potential of these substances was evaluated using the microcombustion calorimeter. Results demonstrated that both heat release reduction potential and char formation were structure dependent. Some of the compounds containing an aromatic core had more effect on char formation (higher char yields) and peak heat-release rate (lowered heat release) than just phosphorus content alone.

Study of using aluminum hypophosphite as a flame retardant for low-density polyethylene


Aluminum hypophosphite (AHP) was first used to improve the flame retardance of low-density polyethylene (LDPE). The flame-retardant properties of LDPE composites were investigated by the limiting oxygen index, vertical burning test (UL-94), microscale combustion calorimetry, and cone calorimeter tests. The results showed that the incorporation of AHP could improve the flame retardancy of LDPE dramatically, the limiting oxygen index of LDPE containing 50 phr AHP reached 27.5%, and the UL-94 could pass V-0 rating. The cone calorimeter test results indicated that PP/AHP composite exhibited superior performance, and the heat release rate and the total heat release of composites were significantly reduced. In addition, the strength of the char was improved with the load of AHP increased. The structure of the char was researched by Fourier transform infrared spectrometry (FTIR) and scanning electron microscope-energy dispersive spectrometer, and the results revealed that AHP promoted the formation of compact char layer. The TG-FTIR analyses proved that AHP could react with LDPE to reduce the production of olefin in gas phase. Moreover, the structure of P–O–C was found, and the effective mechanism of AHP in LDPE composites was also hypothesized in this work.

Poly(vinyl chloride) and its fire properties


This work provides an up-to-date review of the fire properties of poly(vinyl chloride) (PVC) materials, both rigid (unplasticized) and flexible (plasticized). The fire properties addressed include ignitability, ease of extinction (oxygen index), flame spread (small scale and intermediate scale), heat release, smoke obscuration, smoke toxicity, hydrogen chloride emission and decay, and performance in real-scale fires. This comprehensive review includes a wide selection of references and tables illustrating the properties of PVC materials in comparison with those of other polymeric materials, including, in many instances, wood materials. The work puts these fire properties in perspective, showing that the heat release rate (the key fire property) of rigid PVC (and that of properly flame-retarded flexible PVC) are among the lower values found for combustible materials. This work also shows that the smoke toxicity and smoke obscuration resulting from burning PVC materials in real-scale fires is in the same range as those of other materials.

Measurement of self-heating potential of biomass pellets with isothermal calorimetry


To assess the risk for spontaneous combustion of biomass pellets during storage, it is important to know how prone the fuel is to self-heating, ie, to determine the reactivity. This article presents the results from isothermal calorimetry tests performed on 31 different biomass pellet batches. The purpose of the tests has been to characterize pellets by measuring the reactivity and investigate how the pellet composition influences the heat release rate (HRR) and thereby the self-heating potential of pellets. The results from the tests clearly indicate that there is a significant difference in reactivity between different types of pellets. The tested high reactive pellet batches reached maximum specific HRRs (HRRmax) of 0.61 to 1.06 mW/g while pellet batches with low reactivity showed HRRmax of 0.05 to 0.18 mW/g. The tested batches were primarily ranked on the basis of HRRmax, but an alternative ranking based on specific total heat release rate (THR) during the test period was also used for comparison. The test results also indicate that pine/spruce mix pellets are significantly more reactive than all other types of pellets tested and that pellets consisting of 100% pine are more reactive than pellets consisting of 100% spruce. Pellets produced from wine pruning/grape pomace (winery wastes), straw, or eucalyptus are not very reactive compared to pellets consisting of pine/spruce. The results also show that the reactivity of the pellets can be reduced either by introducing certain kinds of antioxidants into the pellets or by extracting lipids from the raw material of pellets.

Crack evolution process of window glass under radiant heating


Window glass breakage has a significant impact on the compartment fire development being sometimes a weak link for fire safety design. This work focuses on the process of crack evolution of window glass in a fire environment. A total of 11 experiments were conducted in a box apparatus by changing heating rate of a heat source. The box apparatus is an enclosed compartment, which includes the heat source, assembled boxes, and glass pane. Crack time, temperature field, breaking stress, crack evolution, and fall-out of the glass panes are presented. Main and secondary fractures are defined and illustrated in the process of crack evolution. Average time to the first, second, and third main fractures decreased as the heating rate of heat source increased. The average breaking stress was 71.14 MPa for float glass at the time of first main fracture. The crack evolution process was very complicated. Cracks initiated at an edge and propagated towards other edges for main fractures. Multiple cracks were joined together to form cracked glass islands. The fall-out of cracked glass islands under radiant heating was more difficult than that under real fire scenarios.

Study on different finite difference methods at skin interface for burn prediction in protective clothing evaluation


For protective clothing evaluation by using the flame engulfment method, a skin burn injury model is required to predict burn degree of the covered skin. By applying finite difference methods, 2 numerical methods are compared. One is based on equivalent heat intensity; the other is based on the law of conservation of energy. In this study, skin temperature rise is compared between these 2 methods by using homogeneous skin properties as well as the analytical solutions. Differences between these 2 methods in application of measured heat exposure tests data are also explored. The results show that assuming equivalent heat intensity at the skin layer interfaces overestimates severity of burn injury. Burn injury time is sensitive to the investigated numerical methods, especially for third-degree burns. The differences of the 2 methods can be reduced by optimization of the grid size using the test cases described in ASTM F1930. A detailed description of requirements regarding applicable numerical methods in future revisions of the relevant standards is recommended. The finite difference model applied in this paper can act as an effective tool to predict temperature distribution in the skin as well as predict burn injury for evaluation of thermal protective clothing.

Tensile properties of plant fibre-polymer composites in fire


The structural performance of polymer composites reinforced with plant fibres when exposed to fire was experimentally evaluated and compared against an E-glass fibre laminate. Fire testing under combined one-sided radiant heating and static tensile loading revealed that flax, jute, or hemp fibre composites experience more rapid thermal softening and fail within much shorter times than the fibreglass laminate, which is indicative of vastly inferior structural performance in fire. The plant fibre composites soften and fail before the onset of thermal decomposition of the plant fibres and polymer matrix, whereas the E-glass fibres provide the composite with superior tensile properties to higher temperatures and higher applied tensile stresses. The tensile performance of the three types of plant fibre composites in fire was not identical. When exposed to the same radiant heat flux, the flax fibre composite could withstand higher tensile stresses for longer times than the hemp and jute laminates, which showed similar performance.

Thermal degradation and fire performance of wood treated with PMUF resin and boron compounds


Plantation Chinese fir wood was modified by low molecular weight phenol melamine urea formaldehyde (PMUF) resin, boron compounds (BB), and the mixture of PMUF/BB (PMUF-BB), followed by a curing step. The fire performance and thermal degradation of wood was measured by limiting oxygen index instrument, cone calorimeter, and simultaneous thermal analysis. The results showed that the limiting oxygen index increased to 50.7%, 43.5%, and 55.0% for BB, PMUF, and PMUF-BB samples, respectively. The PMUF resin decreased the heat release rate of wood but increased the total heat release compared with the control samples. The thermal analysis results demonstrated that PMUF resin enhanced the thermal stability of wood, however, had little impact on the residual chars. Combinative treatment with boron compounds could substantially reduce the fire risk for PMUF-modified wood, making them especially useful for application in public settings.

Procedures for development and revision of codes and standards associated with fire safety in the USA


The process of codes and standards development, and subsequent regulation, in the USA is very different from that in most other countries: it is managed by private (not-for-profit) companies and is via a consensus process. With regards to codes, primary code development occurs through International Code Council (ICC), for building, fire, and mechanical codes, and National Fire Protection Association (NFPA), for electrical and life safety codes. With regards to standards, the key fire test standards used in codes are also developed by companies, primarily American Society for Testing and Materials (ASTM) International and NFPA. All meetings at which codes and standards are developed are open to interested parties and/or observers. This study describes the way the major codes and standards are developed and amended, by the organizations referenced. Participation by all stakeholders is strongly encouraged, and the opinions of any interested parties are an essential component of the process. However, producers (or manufacturers) cannot represent more than a fraction of voting members in the committees and, in fact, in the case of ICC, only public officials are permitted to vote on the final action. At ASTM, technical committees are created by the organization and anyone can become a member. However, voting is restricted and balanced to ensure that producers cannot be a majority. No codes are developed by ASTM. Each committee chooses its projects to develop standards, within an overall scope; committee membership is not limited. The technical committee handling fire issues is ASTM E05, but other committees also develop fire test standards and specifications, including fire tests. At NFPA, technical committees are formed, and its members appointed, by the NFPA Standards Council, and committees are kept small. Appointments are made based on technical expertise and interest categories (one of which is manufacturers). Members in none of the interest categories can exceed one third of the committee membership. Every committee decision can be appealed (commented on), and the committee must consider the comments. The committee decisions can be appealed again, and the issues are debated in front of the general membership at meetings. Fire tests are issued by the technical committee on fire tests, while other committees deal with various codes and standards that can be adopted for regulation, including the National Electrical Code (NEC) (NFPA 70) and the Life Safety Code (NFPA 101). Most technical committees deal with a single document, but the technical committee on fire tests deals with all the fire test methods. In contrast, multiple committees handle separate sections of the major codes. Virtually, the entire country adopts the NEC and many states (as well as the healthcare industry) adopt NFPA 101. Almost all of the major codes with fire implications are developed at ICC. This includes the International Building Code, Internation[...]

Characterization of arc beads on energized conductors exposed to radiant heat


It has been discovered through experimentation the mechanism of how and when an arcing short or a physical short occurs on a cable when exposed to a radiant heat flux. It is then considered how this mechanism acts on the size of the resulting arc beads. Another discovery was that a leakage current precedes a short circuit. Subsequently, it was found that arcing shorts and physical shorts can be distinguished based on the amount of leakage current that precedes the short circuit. In the case of an arcing short, the leakage current is large and the arc bead is small. The opposite is true for a physical short. In the case of a physical short, the leakage current is small and the arc beads are large. Tests were conducted with a Japanese polyvinyl chloride (PVC)–insulated sheathed cable, an American PVC–sheathed non-metallic (NM) cable, and an American cloth–sheathed NM cable. The following were found: A Japanese PVC–insulated sheathed cable tends to cause a physical short and to form larger arc beads than other cables. American NM cables tend to cause an arcing short. Especially, an American cloth–insulated cable tends to be preceded by a larger leakage current and to form smaller arc beads than other cables. This result corresponds to the experimental description in NFPA 921 concerning arc beads on a cloth-sheathed NM cable.