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5769 KiB

Open AccessArticle

Characterization of Thermo-Physical Properties of EVA/ATH: Application to Gasification Experiments and Pyrolysis Modeling

by Bertrand Girardin, Gaëlle Fontaine, Sophie Duquesne, Michael Försth and Serge Bourbigot

Materials 2015, 8(11), 7837-7863; https://doi.org/10.3390/ma8115428 - 20 Nov 2015

Cited by 26 | Viewed by 7323

Abstract

The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the [...] Read more.

The pyrolysis of solid polymeric materials is a complex process that involves both chemical and physical phenomena such as phase transitions, chemical reactions, heat transfer, and mass transport of gaseous components. For modeling purposes, it is important to characterize and to quantify the properties driving those phenomena, especially in the case of flame-retarded materials. In this study, protocols have been developed to characterize the thermal conductivity and the heat capacity of an ethylene-vinyl acetate copolymer (EVA) flame retarded with aluminum tri-hydroxide (ATH). These properties were measured for the various species identified across the decomposition of the material. Namely, the thermal conductivity was found to decrease as a function of temperature before decomposition whereas the ceramic residue obtained after the decomposition at the steady state exhibits a thermal conductivity as low as 0.2 W/m/K. The heat capacity of the material was also investigated using both isothermal modulated Differential Scanning Calorimetry (DSC) and the standard method (ASTM E1269). It was shown that the final residue exhibits a similar behavior to alumina, which is consistent with the decomposition pathway of EVA/ATH. Besides, the two experimental approaches give similar results over the whole range of temperatures. Moreover, the optical properties before decomposition and the heat capacity of the decomposition gases were also analyzed. Those properties were then used as input data for a pyrolysis model in order to predict gasification experiments. Mass losses of gasification experiments were well predicted, thus validating the characterization of the thermo-physical properties of the material. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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6238 KiB

Open AccessArticle

Controlled Emissivity Coatings to Delay Ignition of Polyethylene

by Rodolphe Sonnier, Laurent Ferry, Benjamin Gallard, Abderrahim Boudenne and François Lavaud

Materials 2015, 8(10), 6935-6949; https://doi.org/10.3390/ma8105349 - 12 Oct 2015

Cited by 14 | Viewed by 7532

Abstract

Semi-opaque to opaque films containing small amounts of various aluminium particles to decrease emissivity were easily prepared and coated onto low-density polyethylene (LDPE) sheets. The thermal-radiative properties (reflectivity, transmissivity and absorptivity) of the films were measured and related to the aluminum particles’ content, [...] Read more.

Semi-opaque to opaque films containing small amounts of various aluminium particles to decrease emissivity were easily prepared and coated onto low-density polyethylene (LDPE) sheets. The thermal-radiative properties (reflectivity, transmissivity and absorptivity) of the films were measured and related to the aluminum particles’ content, size and nature. Time-to-ignition of samples was assessed using a cone calorimeter at different heat flux values (35, 50 and 75 kW/m²). The coatings allowed significant ignition delay and, in some cases, changed the material behaviour from thermally thin to thick behaviour. These effects are related both to their emissivity and transmissivity. A lower emissivity, which decreases during the degradation, and a lower transmissivity are the key points to ensure an optimal reaction-to-fire. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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8845 KiB

Open AccessArticle

Pyrolysis Model Development for a Multilayer Floor Covering

by Mark B. McKinnon and Stanislav I. Stoliarov

Materials 2015, 8(9), 6117-6153; https://doi.org/10.3390/ma8095295 - 14 Sep 2015

Cited by 35 | Viewed by 7637 | Correction

Abstract

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design [...] Read more.

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m⁻², which is within the mean experimental uncertainty. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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4823 KiB

Open AccessArticle

Influence of Flame Retardants on the Melt Dripping Behaviour of Thermoplastic Polymers

by Melissa Matzen, Baljinder Kandola, Christian Huth and Bernhard Schartel

Materials 2015, 8(9), 5621-5646; https://doi.org/10.3390/ma8095267 - 27 Aug 2015

Cited by 64 | Viewed by 8018

Abstract

Melt flow and dripping of the pyrolysing polymer melt can be both a benefit and a detriment during a fire. In several small-scale fire tests addressing the ignition of a defined specimen with a small ignition source, well-adjusted melt flow and dripping are [...] Read more.

Melt flow and dripping of the pyrolysing polymer melt can be both a benefit and a detriment during a fire. In several small-scale fire tests addressing the ignition of a defined specimen with a small ignition source, well-adjusted melt flow and dripping are usually beneficial to pass the test. The presence of flame retardants often changes the melt viscosity crucially. The influence of certain flame retardants on the dripping behaviour of four commercial polymers, poly(butylene terephthalate) (PBT), polypropylene (PP), polypropylene modified with ethylene-propylene rubber (PP-EP) and polyamide 6 (PA 6), is analysed based on an experimental monitoring of the mass loss due to melt dripping, drop size and drop temperature as a function of the furnace temperature applied to a rod-shaped specimen. Investigating the thermal transition (DSC), thermal and thermo-oxidative decomposition, as well as the viscosity of the polymer and collected drops completes the investigation. Different mechanisms of the flame retardants are associated with their influence on the dripping behaviour in the UL 94 test. Reduction in decomposition temperature and changed viscosity play a major role. A flow limit in flame-retarded PBT, enhanced decomposition of flame-retarded PP and PP-EP and the promotion of dripping in PA 6 are the salient features discussed. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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980 KiB

Open AccessArticle

On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials

by Pascal Boulet, Damien Brissinger, Anthony Collin, Zoubir Acem and Gilles Parent

Materials 2015, 8(8), 5398-5413; https://doi.org/10.3390/ma8085251 - 21 Aug 2015

Cited by 28 | Viewed by 5080

Abstract

The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon [...] Read more.

The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90–0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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2780 KiB

Open AccessArticle

The Effects of Thermophysical Properties and Environmental Conditions on Fire Performance of Intumescent Coatings on Glass Fibre-Reinforced Epoxy Composites

by Baljinder K. Kandola, Piyanuch Luangtriratana, Sophie Duquesne and Serge Bourbigot

Materials 2015, 8(8), 5216-5237; https://doi.org/10.3390/ma8085216 - 11 Aug 2015

Cited by 34 | Viewed by 6614

Abstract

Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable [...] Read more.

Intumescent coatings are commonly used as passive fire protection systems for steel structures. The purpose of this work is to explore whether these can also be used effectively on glass fibre-reinforced epoxy (GRE) composites, considering the flammability of the composites compared to non-flammable steel substrate. The thermal barrier and reaction-to-fire properties of three commercial intumescent coatings on GRE composites have been studied using a cone calorimeter. Their thermophysical properties in terms of heating rate and/or temperature dependent char expansion ratios and thermal conductivities have been measured and correlated. It has been suggested that these two parameters can be used to design coatings to protect composite laminates of defined thicknesses for specified periods of time. The durability of the coatings to water absorption, peeling, impact, and flexural loading were also studied. A strong adhesion between all types of coatings and the substrate was observed. Water soaking had a little effect on the fire performance of epoxy based coatings. All types of 1 mm thick coatings on GRE helped in retaining ~90% of the flexural property after 2 min exposure to 50 kW/m² heat flux whereas the uncoated laminate underwent severe delamination and loss in structural integrity after 1 min. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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797 KiB

Open AccessArticle

Important Parameter Groups in Thermal Protection of Polymers

by John Staggs

Materials 2015, 8(8), 4679-4698; https://doi.org/10.3390/ma8084679 - 24 Jul 2015

Cited by 3 | Viewed by 4205

Abstract

The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed [...] Read more.

The problem of thermal protection is explored for two idiosyncratic reactive systems, namely a sacrificial heat-sink material and an intumescent system where a dynamically evolving insulation layer is produced from an initially thin coating. Relatively simple mathematical models of both systems are proposed that encompass the important physical characteristics of each situation and these models are analysed using a mixture of numerical and analytical techniques. Important dimensionless parameter groups are identified and domains of parameter space where thermal performance is particularly good- or particularly bad- are identified. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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1420 KiB

Open AccessArticle

Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate)

by Fei Peng, Xiao-Dong Zhou, Kun Zhao, Zhi-Bo Wu and Li-Zhong Yang

Materials 2015, 8(7), 4004-4021; https://doi.org/10.3390/ma8074004 - 2 Jul 2015

Cited by 13 | Viewed by 5539

Abstract

In this work, the effect of seven different sample orientations from 0° to 90° on pilot and non-pilot ignition of PMMA (poly(methyl methacrylate)) exposed to radiation has been studied with experimental and numerical methods. Some new and significant conclusions are drawn from the [...] Read more.

In this work, the effect of seven different sample orientations from 0° to 90° on pilot and non-pilot ignition of PMMA (poly(methyl methacrylate)) exposed to radiation has been studied with experimental and numerical methods. Some new and significant conclusions are drawn from the study, including a U-shape curve of ignition time and critical mass flux as sample angle increases for pilot ignition conditions. However, in auto-ignition, the ignition time and critical mass flux increases with sample angle α. Furthermore, a computational fluid dynamic model have been built based on the Fire Dynamics Simulator (FDS6) code to investigate the mechanisms controlling the dependence on sample orientation of the ignition of PMMA under external radiant heating. The results of theoretical analysis and modeling results indicate the decrease of total incident heat flux at sample surface plays the dominant role during the ignition processes of auto-ignition, but the volatiles gas flow has greater influence for piloted ignition conditions. Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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159 KiB

Open AccessCorrection

Correction: McKinnon M.B. and Stoliarov S.I. Pyrolysis Model Development for a Multilayer Floor Covering. Materials 2015, 8, 6117–6153

by Mark B. McKinnon and Stanislav I. Stoliarov

Materials 2015, 8(11), 7587-7588; https://doi.org/10.3390/ma8115402 - 11 Nov 2015

Viewed by 3882

Abstract

The authors wish to make the following corrections to this manuscript [1]. During the publishing process, symbols that represented the absorption coefficient in Table 4 and thermal conductivity in Table 5 were changed such that they were inconsistent with the rest of the [...] Read more.

The authors wish to make the following corrections to this manuscript [1]. During the publishing process, symbols that represented the absorption coefficient in Table 4 and thermal conductivity in Table 5 were changed such that they were inconsistent with the rest of the manuscript. [...] Full article

(This article belongs to the Special Issue Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers)

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