Application of cone calorimeter for the assessment of class of flame retardants for polypropylene

The study presented addresses the fire behaviour of polypropylene compounded with six classes of flame retardants. The application of cone calorimetry for the assessment of the thermal characteristics of the tested materials and their comparison with thermogravimetry are the central point of this research. This study only presents data for 25 kW/m² of incident heat flux exposure and includes five tests for polypropylene with no additives and five tests for polypropylene with flame retardants based on triglycidylisocyanurate and lignin. The data collected include the rate of heat release, mass loss rate, char yield, time to ignition and time of total combustion. Results represent meaningful comparison between the behaviour of the materials under simulated fire conditions, using the cone calorimeter, and in the slow dynamic environment utilized in thermogravimetric analysis. © 1998 John Wiley & Sons Ltd.     

Influence of fire retardants on the reaction‐to‐fire properties of coextruded wood–polypropylene composites

The reaction‐to‐fire properties of coextruded wood–plastic composites containing different fire retardants (melamine, zinc borate, ammonium polyphosphate, aluminium trihydroxide, natural flake graphite and expandable graphite) in the shell layer have been studied with the cone calorimetry technique. The effect of ammonium polyphosphate in combination with graphite has also been studied with a cone calorimeter test. A coextruded composite manufactured without any fire retardant addition has been used as a reference. The fire properties measured in the cone calorimeter are discussed, including the heat release rate, total heat release, smoke production, specific extinction area, CO yield and mass loss rate. The results show that the introduction of fire retardants in the shell layer of coextruded wood–polypropylene composites has a favourable effect on the fire resistance properties of the composite materials. The reaction‐to‐fire properties have been improved according to the fire classification of construction products based on the Euroclass system. Copyright © 2015 John Wiley & Sons, Ltd.     

The rapid mass calorimeter: A route to high throughput fire testing

The rapid mass calorimeter based on reduced‐size specimens is proposed for accelerated fire testing and put up for discussion, particularly for flame retarded polymeric materials. A mass loss calorimeter is combined with a semiautomatic sample changer. Experiments on specimens of reduced size were conducted on poly(methyl methacrylate), poly(propylene), polyamide 66, poly(ether ether ketone), and pine sapwood square samples with edge lengths of 100, 75, 50, 25, 20, and 10 mm. Specimens of 20 × 20 mm² were selected to achieve a crucial reduction in specimen size and a measuring protocol developed. A total of 71 different polymeric materials were investigated in the rapid mass calorimeter and cone calorimeter for comparison and several materials with different heat release rate characteristics in the pyrolysis combustion flow calorimeter to test this additional screening method as well. The important fire properties obtained in the rapid mass calorimeter show reasonable correlation with the cone calorimeter results but also with the oxygen index. All in all, the rapid mass calorimeter produces reliable and meaningful results and, despite acceleration and size reduction, still allows for a certain degree of burning behavior interpretation. Material savings of 96% and time savings of around 60%‐70% are achieved compared to measure cone calorimeter.     

Combustion characteristics of cellulosic loose fibres

The aim of this paper is to study the combustion characteristics of loose fibrous cellulosic compounds through cone calorimeter measurements. The challenge in studying loose fibrous materials by cone calorimeter in a reproducible manner is met by optimizing various process parameters such as sample weight, heat flux and grid type. The method is validated using cotton fibres and fabrics with a range of flame retardant properties. Good correlations are obtained between the flame retardant content of samples and the heat release parameters for both the fibres and the fabrics. In addition, fibres from specific cotton cultivars showed statistically significant differences in heat release characteristics. This shows that valuable data concerning the combustion behaviour and the corresponding kinetics of loose fibrous compounds can be successfully gathered using a cone calorimeter. Thus, such data can be exploited to well define future fibre breeding programmes or fibre modification research. Copyright © 2012 John Wiley & Sons, Ltd.     

The Accumulation of Flammable Gases in Cone Calorimeter Tests is Responsible for Flash Ignition of Wool and Cotton Samples

In this paper a possible explanation is presented for the differences found between the fire behaviour of materials in small-scale cone calorimeter tests and the large-scale furniture calorimeter. The results obtained with cone calorimeter/FTIR equipment at 35 kW m⁻² will show that the early flash ignitions of typical materials like cotton and wool are due to the liberation of flammable gases during the pyrolysis phase and the typical ignition situation on the cone calorimeter, that is, the presence of a sparking igniter above the sample. This fast flash ignition and the early heat release behaviour on the cone calorimeter may be in contradiction to the early fire growth in other fire tests where the ignition conditions are clearly different from pyrolysis circumstances, that is, ignition via a burning newspaper, match, gas flame, etc.     

A milligram-scale flame calorimeter pyrolyzer system used to emulate burning of nonthermally thin solid samples

A new Milligram-scale Flame Calorimetry (MFC) pyrolyzer system was developed to approximate heating conditions experienced by material samples in gram-scale tests, such as cone calorimetry. The main features of this pyrolyzer system are a miniature flat heating coil embedded into a platform supporting the sample crucible. The use of a constant power rather than a constant heating rate operation mode distinguished the new MFC from the other mg-scale flammability test method—microscale combustion calorimetry (MCC). A series of tests was carried out using the new MFC, cone, and MCC on five synthetic polymers representing a wide range of flammability behavior. All methods produced similar solid residue yields. The MFC peak heat release rate (HRR) was found to correlate linearly with the cone peak HRR (R² = 0.93). The MCC peak HRR did not exhibit a strong correlation with the corresponding cone data. The new MFC was found to produce heat of combustion (HOC) values nearly identical to those measured in cone calorimetry. The MCC had a tendency to produce higher heats of combustion. Both MFC and MCC measured sample ignition temperatures that showed some correlation with the square root of the time to ignition measured in a cone calorimeter. The MFC airborne particular yield was found to correlate well (linear R² = 0.91) with the average specific extinction area measured in the cone tests. It was concluded that the newly designed MFC can deliver relatively accurate flammability measurements similar to cone calorimetry while using three orders of magnitude smaller samples.     

On non‐combustibility of commercial building materials

Non‐combustibility is discussed on the basis of experimental data for 66 commercial building materials obtained from two standard test methods: EN ISO 1716 oxygen bomb calorimeter and EN ISO 1182 cylindrical furnace. The sample materials are divided into five categories: concrete and ceramics, thermal/acoustic insulation materials, wall or ceiling boards, mortars and adhesives and thin coatings. To better distinguish between non‐combustible and combustible materials, an effective modified heat of combustion is defined and calculated for all materials tested in both methods. The materials studied exhibited very different mass loss values and a low tendency to auto‐ignite in the cylindrical furnace. Revised criteria for class A1 are proposed for better accuracy of reaction‐to‐fire assessment. It is proposed to use the oxygen bomb calorimeter with only one limit for the heat of combustion, that is, a value of 5 MJ/kg for all materials. The proposed approach is a very efficient tool for fast and inexpensive screening for non‐combustibility of building products and is expected to be a more precise method to distinguish between non‐combustible and combustible materials. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of passenger train car materials in the cone calorimeter

Recent advances in fire test methods and hazard analysis techniques make it useful to re‐examine passenger train fire safety requirements. The use of test methods based on heat release rate (HRR), incorporated with fire modelling and hazard analysis, could permit the assessment of potential hazards under realistic fire conditions. The results of research directed at the evaluation of passenger train car interior materials in the cone calorimeter are presented. These measurements provide data necessary for fire modelling as well as quantitative data that can be used to evaluate the performance of component materials and assemblies. The cone calorimeter test data were also compared with test data resulting from individual bench‐test methods specified in the FRA fire safety guidelines. The majority of the tested materials which meet the current FRA guidelines show comparable performance in the cone calorimeter. Copyright © 1999 John Wiley & Sons, Ltd.     

A model for the pyrolysis of two Nordic structural timbers

Performance-based design of the timber structures' fire resistance is often based on the reduced cross section and thus relying on empirical and numerical assessment of the charring propagation. The current work aims to construct models for the pyrolysis of spruce and pinewoods to allow coupled simulations of the cross-section reduction and burning rate in fire models. Kinetic models are formulated based on thermogravimetric data and supported by the heats of pyrolysis and combustion measurements by differential scanning calorimetry and microscale combustion calorimetry, respectively. The results from these small-scale measurements are consistent with each other, and the heats of pyrolysis and combustion are determined for the wood primary components by fitting the simulations to the experimental results. Heat release models are constructed based on the small-scale tests, and cone calorimeter experiments are used for the estimation of the physical properties and for the heat release model validation.     

Effect of glass fibres and fire retardant on the combustion behaviour of composites,glass fibres–poly(butylene terephthalate)

The oxygen index (OI) of poly(butylene terephthalate) (PBT) tends to decrease when it is combined with milled-glass fibres either with or without the sizing treatment. This shows that the previously found apparent increase of flammability of PBT glass fibre composites (GFPBT) as compared to PBT is not due to the introduction of the flammable sizing together with the glass fibres in the polymer which was one suggested explanation in the literature, but rather to the wick and anti-dripping effects of glass fibres. The effectiveness of a typical brominated organic compound-antimony trioxide fire retardant system (FR), as measured by OI, is found to be larger in GFPBT as compared to PBT. A linear increase of the temperature index (TI) of PBT and of GFPBT is observed with increasing concentration of the FR. The fire retardant increases the time to ignite while it decreases the maximum rate of heat release and increases the smoke optical density and CO evolution on burning in the cone calorimeter. The dependence of fire risk and hazard assessement on the combustion model of the combustion test method is discussed for OI and cone calorimeter in the case of PBT, GFPBT and FR corresponding materials. © 1998 John Wiley & Sons, Ltd.     

Effect of flame heat flux on thermal response and fire properties of char‐forming composite materials

This study evaluates the effect of flame heat flux on the prediction of thermal response and fire properties of a char‐forming composite material. A simplified two‐layer flame model was developed and incorporated into a heat transfer thermal model to predict the thermal response and fire reaction characteristics of a burning material. A typical char‐forming material, E‐glass reinforced polyester composite, was used in the study. A cone calorimeter was used to measure the fire reaction characteristics of the composite. The flame heat flux in a cone calorimeter test setup was estimated using the simplified flame model. Thermal response and fire property predictions with and without the effect of flame heat flux were compared with experimental data obtained from the cone calorimeter tests. Results showed that the average flame heat flux of the composite in a cone calorimeter was 19.1 ± 6 kW/m² from model predictions. The flame had a significant effect on the thermal response and fire properties of the composite around the first heat release peak but the effect decreased rapidly afterwards. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of variations in incident heat flux when using cone calorimeter test data for prediction of full‐scale heat release rates of polyurethane foam

The development of methods to predict full‐scale fire behaviour using small‐scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data were obtained using cone calorimeter tests and infrared video‐based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests and in predicting results for thinner foams. Results indicated that because of sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Heat release rate and computer fire modelling vs real‐scale fire tests in passenger trains

The materials and products used in passenger trains may not be the first ignited element, but during the fire development, these materials, especially ceiling linings and wall coverings, contribute significantly to the fire growth. The fire safety requirements in passenger trains consist mainly of bench‐scale tests, with particular focus on the sample geometry, position and fire exposition. When this information is extrapolated to real end use conditions limitations appear. In this paper, a discussion of the use of fire dynamics simulator model and heat release rate experiments in cone calorimeter (bench‐scale test) is presented in order to represent the fire development in a passenger train compartment. For the study, two fire scenarios were selected: (1) the single burning item SBI test (modified) and (2) a passenger train compartment. Initially, the limitations of the assumptions and hypothesis made when producing the model were analyzed and the research team carried out a sensitivity study of the model results considering different grid sizes. In order to validate the model, both bench‐ and full‐scale fire tests were considered based on the results provided by the European research program FIRESTARR. The limitations and uncertainties in the results demonstrate the importance of two basic factors: the incident heat flux in the cone calorimeter tests and the prescribed ignition temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Thermal and combustion behavior of ethylene‐vinyl acetate/aluminum trihydroxide/Fe‐montmorillonite composites

The flammability characterization and synergistic flame‐retardant effect of Fe‐montmorillonite (Fe‐OMT) in the ethylene‐vinyl acetate/aluminum hydroxide (EVA/ATH) compounds were studied using limiting oxygen index (LOI), UL‐94 test, cone calorimeter, microscale combustion calorimetry (MCC), and thermogravimetric analysis (TGA). The results showed that addition of Fe‐OMT increases the LOI value and improves the UL 94 rating. Cone calorimeter data indicate that the addition of Fe‐OMT greatly reduced the heat release rate and carbon monoxide production rate. Furthermore a compact char residue formed on the surface of the sample with a suitable of Fe‐OMT during the combustion. The MCC results indicate that addition of Fe‐OMT reduced the heat release rate and catalyzed the decomposition of EVA. The TGA data showed further evidence that Fe‐OMT can catalyze carbonization reactions. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Combustion behaviour of ethylene vinyl acetate copolymer-based intumescent formulations using oxygen consumption calorimetry

This work compares the fire degradation of ethylene-vinyl acetate 8% copolymer (EVA8) with two flame-retarded formulations, using the cone calorimeter. The first one, EVA8/ammonium polyphosphate (APP) leads to the protection of the material, in the conditions of a fire, by means of blowing up and weak carbonization. The addition of polyamide-6 (PA-6) in EVA8/APP improves the protection by forming an intumescent carbonaceous shield. The fire hazard of the virgin polymer and of the FR systems are quantified, in terms of rate of heat release, weight loss, effective heat of combustion, volume of smoke production and CO and CO₂ production. It assesses the effectiveness of the fire retardant additives APP and APP/PA-6 in EVA8-based materials under simulated real fire test conditions. The respective temperatures of the degradation front are deduced from the weight loss data recorded in the course of the cone calorimeter experiments and the results of the invariant kinetic parameters method applied to the different specimens. The addition of APP/PA-6 in EVA8 leads to a superficial phenomenon; the degradation zone is thus located on the upper volume of the specimen during all the exposure to the heat flux. © 1998 John Wiley & Sons, Ltd.     

Phosphorus‐Containing Polymer Flame Retardants for Aliphatic Polyesters

Polyesters with 9,10‐dihydro‐9‐oxy‐10‐phosphaphenanthrene‐10‐oxide‐containing comonomers are synthesized aiming to improve the flame retardancy of aliphatic polyesters such as poly(butylene succinate) and poly(butylene sebacate). The influence of the chemical structure on the thermal decomposition and pyrolysis is examined using a combination of thermogravimetric analysis (TGA), TGA‐Fourier transform infrared (FTIR) spectroscopy, pyrolysis‐gas chromatography/mass spectrometry, and microscale combustion flow calorimetry. Thermal decomposition pathways are derived and used to select suitable candidates as flame retardants for PBS. The fire behavior of the selected polymers is evaluated by forced‐flaming combustion in a cone calorimeter. The materials show two modes of action for flame retardancy: strong flame inhibition due to the release of a variety of molecules combined with charring in the solid state.     

Fire-hazard assessment of extended-chain polyethylene and aramid composites by cone calorimetry

A cone calorimeter is used to determine the fire performance of polymer composite materials containing combustible reinforcing fibres in addition to combustible matrix resins. Extended-chain polyethylene and aramid fibre-reinforced composites containing epoxy, vinylester and phenolic matrix resins are examined at various cone irradiances. Values for time to ignition, rate of heat release, effective heat of combustion, smoke density and evolved carbon monoxide and carbon dioxide are reported for the reinforcements, matrix resins and composites. The reinforcements have a significant effect on the fire-hazard properties of the composite materials. For the epoxy and vinylester composites, times to ignition reflect those of the component of higher ignitability. This was not the case for the aramid-reinforced phenolic composite, in which the resin surface layer hinders combustion of the fabric reinforcement. Resin and reinforcement contributions to the composite rate of heat release behaviour as a function of time are generally discernible.     

Mechanical properties of fire‐damaged glass‐reinforced phenolic composites

Changes to the mechanical and physical properties of a glass‐reinforced resole phenolic composite due to intense radiant heat and fire are investigated. Fire testing was performed using a cone calorimeter, with the composite exposed to incident heat fluxes of 25, 50, 75 or 100 kW/m² for 325 s and to a constant flux of 50 kW/m² for different times up to 1800 s. The post‐fire tensile and flexural properties were determined at room temperature, and these decreased rapidly with increasing heat flux and heat exposure time due mainly to the chemical degradation of the phenolic resin matrix. The intense radiant heat did not cause any physical damage to the composite until burning began on exposure to a high heat flux. The damage consisted of cracking and combustion of the phenolic matrix at the heat‐exposed surface, but this only caused a small reduction to the mechanical properties. The implication of the findings for the use of glass‐reinforced resole phenolic composites in load‐bearing structures for marine craft and naval ships, where fire is a potential hazard, is discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Combustion characteristics of crude oils

Small‐scale free‐burning pool fire tests were conducted in a cone calorimeter to obtain the combustion characteristics of 14 different crude oils. Measurements included the heat release rate based on oxygen consumption calorimetry, mass loss rate, radiative heat flux from the flame to a nearby target, liquid fuel temperature, extinction coefficient and CO₂ and CO concentrations in the exhaust duct. The effective heat of combustion, radiative heat loss fraction and smoke yield were calculated on the basis of the measured data. It was found that the heat release rate, mass loss rate, flame radiation and smoke yield were a function of the type of crude oil. The effective heat of combustion, extinction coefficient and radiative heat loss fraction were nearly constant for the range of crude oils evaluated in this programme. The heat release rate, mass loss rate, flame radiation and smoke yield appeared to correlate well with the crude oil density. Copyright © 2001 John Wiley & Sons, Ltd.     

Effect of curprous oxide in combination with molybdenum trioxide on smoke suppression in rigid poly(vinyl chloride)

Further investigation of the synergistic effect of smoke suppression between cuprous oxide and molybdenum trioxide in rigid poly(vinyl chloride) (PVC) was carried out by using a cone calorimeter (cone) at a high incident heat flux of 50 kW m^?2. Experimental data derived from the cone calorimeter indicated that binary mixtures of Cu₂O and MoO₃ clearly showed the synergistic effect in reducing smoke by decreasing total smoke production (TSP), average specific extinction area (av‐SEA), and smoke production rate (SPR). This result is in good agreement with that obtained from the NBS smoke chamber. However, the combustion process of rigid PVC could clearly be seen from the heat release rate (HRR), curve, SPR, and fire degradation obtained from the cone test, which could not be determined from the NBS smoke chamber. It was also found that the binary mixture showed the synergistic effect by increasing was also found that the binary mixture showed the synergistic effect by increasing char residue and reducing the fire degradation of the PVC backbone at a high incident heat flux of 50 kW.m^?2. All experimental data well supported the early cross‐linking mechanism of the PVC backbone mentioned in the literature and were consistent with the fire degradation behavior obtained from the cone calorimeter.