Cone Calorimeter Experiments Research Articles

Flammability and thermal stability studies of ABS/Montmorillonite nanocomposite

AbstractAcrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry

Flammability and phase-transition studies of nylon 6/montmorillonite nanocomposites

Nylon 6 (PA6)/clay hybrids have been prepared using a direct melt intercalation technique by two processes. One is PA6 melt-mixing with modified clay, the other is PA6 melt-mixing with natural (Na+ base) clay using an ammonium salt bearing long alkyl chains as a polymer/clay reactive compatibilizer. Their structure and flammability properties are characterized by X-ray diffraction, transmission electron microscopy and cone calorimeter experiments. The results of the cone calorimeter experiments show that hybrids made by these two processes have a lower heat release rate peak and higher thermal stability than that of original PA6. Meanwhile, X-ray diffraction was used to investigate PA6/clay hybrids with various cooling histories from the melt, including medium-rate cooling (air cooling) and rapid cooling (water-quenched). In contrast to pure PA6 dominated by the α phase, the addition of clay silicate layers by these two methods favors the formation of the γ crystalline phase in PA6/clay hybrids. Flammability and phase-transition studies confirm that silicate layers added by these two methods have a similar nanoeffect and nanodispersion in the PA6 matrix.

Preparation and Combustion Properties of Flame Retardant Nylon 6/Montmorillonite Nanocomposite

AbstractFlame retardant Nylon 6 (PA6)/montmorillonite (MMT) nanocomposites have been prepared using direct melt intercalation technique by blending PA6, organophilic clay and conventional fire retardants, such as the melamine cyanurate (MCA) and the combination of decabromodiphenyl oxide (DB) and antimony oxide (AO). Their morphology and combustion properties are characterized by XRD, transmission electron microscopy (TEM), UL‐94 test and Cone Calorimeter experiments. The flame retardant nanocomposites with MCA or DB and AO show lower heat release rate (HRR) peak compared to that of conventional flame retardant PA6. Meanwhile, the synergetic effect was studied between clay and DB‐AO.TEM of PA‐n nanocomposite.magnified imageTEM of PA‐n nanocomposite.

Flame Retardancy of Laponite- and Montmorillonite-Based Nylon 6 Nanocomposites

ABSTRACTThe flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.

Combustion characteristics of asphalt and sodium compounds

Abstract Risk evaluation of mixtures of asphalt and inorganic salts such as sodium nitrate, sodium nitrite, sodium carbonate and sodium dihydrogenphosphate was conducted. The ignition and the combustion characteristics of mixtures of asphalt and oxidizing salts were obtained. Quasi-heat-accumulation experiments of asphalt–salt mixtures were conducted using about 1 kg samples. Six types of asphalt–salt mixtures were made and their ignition characteristics were examined in the quasi-heat-accumulation experiments. Then to clarify burning behavior of the asphalt–salt mixtures, experiments for understanding their combustion characteristics were conducted using a cone calorimeter. The main results are as follows. (1) In the quasi-heat-accumulation experiment, a region with high concentration of the salt mixture particles was made at the bottom of the sample vessel through the process of their sedimentation. An exothermic reaction started in this region. Just before the asphalt–salt mixture was ignited, a huge amount of white smoke was released. A kind of jet flame of a few meters in height was created. (2) Based on the data of ignition temperature from the cone calorimeter experiments, ignition of asphalt was caused by a chemical reaction of asphalt with an oxidizing salt. The combustion of the asphalt–salt mixture contained the self-heating reaction.

Rheological investigations in fire retardancy: application to ethylene-vinyl-acetate copolymer-magnesium hydroxide/zinc borate formulations

In this work, zinc borate is used as synergistic agent in EVA-Mg(OH) 2 flame-retardant (FR) formulations. High zinc borate content leads to a significant improvement of flame retardancy during cone calorimeter experiments. Blowing measurements reveal significant modification of the structure due to the presence of zinc borate. To estimate the resistance of this structure under strength, blowing measurements were carried out under two different pressures. Viscosity measurements helped to elucidate the foamine process. Finally, zinc borate can he understood to be a hinder (flux agent).

Recent advances in the use of zinc borates in flame retardancy of EVA

In this work, zinc borates are used as synergistic agents in EVA–ATH and EVA–Mg(OH) 2 flame-retardant (FR) formulations and as smoke suppressants. Moreover, the study by solid state NMR of the residues sampled at different times during cone calorimeter experiments of the formulations EVA–ATH and EVA–ATH/Zinc borate allows to propose a mechanism of action of the FR systems. It is demonstrated that the decomposition of Aluminium trihydroxide (ATH) to Al 2O 3 during the heating of the polymer results in an increase of the ignition time. Moreover the formation of Al 2O 3 in situ from ATH during the combustion of the polymer is the first event. Concurrently zinc borate degrades and it is proposed that a vitreous protective coating is created, which yields a more efficient char.

Modelling the combustion of solid-phase fuels in cone calorimeter experiments

The process of ablation often forms a key part in many mathematical models describing the combustion of a solid-phase fuel. The phrase was first used to describe the thermal erosion of glaciers over 140 years ago. In recent times it has been applied to the thermal degradation of a solid when exposed to a large flux of heat. Two fundamental assumptions in the treatment are that mass is lost only from surface regions and that the temperature of the surface remains constant throughout the period of mass loss. The two critical parameters in this model are the critical temperature Tp at which mass loss occurs and the heat required to convert matter from solid to gas at temperature Tp. In this paper we report mathematical models designed to simulate the loss of mass of a solid fuel (such as polyethylene) in cone calorimeter experiments. The models do not compromise on the thermal properties of the solid fuel or the heat loss mechanisms and consequently they require a numerical method of solution. Initially we explore a relatively simple ablation-based model. Although conceptually simple in approach, the model reproduces many qualitative features observed in experiments. We go on to consider a different approach, where the thermal degradation of the solid is governed by a set of kinetic rate laws. We show that this approach removes many of the unrealistic features and assumptions of ablation-based models. Furthermore, we demonstrate that the agreement between theory and experiment is improved by this approach. We also show how the mathematical models may be used as aids in the interpretation of cone calorimeter data. For example, we show that a steady state measurement of mass loss rate is a more reliable indicator of a material response than a peak measurement. In fact we show how peak measurements are strongly affected by the thermal properties of the sample holder, but steady state measurements are insensitive to the particular choice of sample holder. Copyright © 1999 John Wiley and Sons, Ltd.

Modelling the combustion of solid‐phase fuels in cone calorimeter experiments

The process of ablation often forms a key part in many mathematical models describing the combustion of a solid-phase fuel. The phrase was first used to describe the thermal erosion of glaciers over 140 years ago. In recent times it has been applied to the thermal degradation of a solid when exposed to a large flux of heat. Two fundamental assumptions in the treatment are that mass is lost only from surface regions and that the temperature of the surface remains constant throughout the period of mass loss. The two critical parameters in this model are the critical temperature Tp at which mass loss occurs and the heat required to convert matter from solid to gas at temperature Tp. In this paper we report mathematical models designed to simulate the loss of mass of a solid fuel (such as polyethylene) in cone calorimeter experiments. The models do not compromise on the thermal properties of the solid fuel or the heat loss mechanisms and consequently they require a numerical method of solution. Initially we explore a relatively simple ablation-based model. Although conceptually simple in approach, the model reproduces many qualitative features observed in experiments. We go on to consider a different approach, where the thermal degradation of the solid is governed by a set of kinetic rate laws. We show that this approach removes many of the unrealistic features and assumptions of ablation-based models. Furthermore, we demonstrate that the agreement between theory and experiment is improved by this approach. We also show how the mathematical models may be used as aids in the interpretation of cone calorimeter data. For example, we show that a steady state measurement of mass loss rate is a more reliable indicator of a material response than a peak measurement. In fact we show how peak measurements are strongly affected by the thermal properties of the sample holder, but steady state measurements are insensitive to the particular choice of sample holder. Copyright © 1999 John Wiley and Sons, Ltd.

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.

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.