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Special Issue "Influence of Thermo-Physical and Thermo-Optical Properties on the Fire Behavior of Polymers"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (31 May 2015)

Special Issue Editors

Guest Editor
Dr. Rodolphe Sonnier

Ecole des Mines d’Alès, Centre des Matériaux des Mines d’Alès (C2MA), 6 Avenue de Clavières, F-30319 Alès Cedex, France
Website | E-Mail
Interests: polymer flammability; flame retardancy; fire testing; ionizing radiation
Guest Editor
Dr. Laurent Ferry

Ecole des Mines d’Alès, Centre des Matériaux des Mines d’Alès (C2MA), 6 Avenue de Clavières, F-30319 Alès Cedex, France
Website | E-Mail
Interests: polymer flammability; thermal degradation; flame retardant; mineral filler; bio-based resources

Special Issue Information

Dear Colleagues,

For several years, some excellent papers have focused on the influence of thermo-physical and thermo-optical properties on polymer flammability. For instance, it has been discovered that bubbling can modify a material’s heat absorption, leading to great changes in heat release rate. Nanoparticles reduce heat absorption in-depth and this phenomenon is believed to explain the decrease in various nanocomposites’ time-to-ignition.

Various strategies have also been proposed to improve flame retardancy by modifying thermal conductivity or reflectivity: some carbon-based fillers can increase the thermal conductivity of materials, thus delaying ignition. High-reflectance coatings have also been proposed as an original strategy for limiting the heating of materials.

Limiting the heat transfer from the flame to the condensed phase by creating an insulating char layer is also the objective of many researchers: this involves the use of phosphorus flame retardants. Pyrolysis at high temperature creates various layers; measuring their thermo-physical properties is still a great challenge.

Finally, modeling the fire behavior of materials provides insight into the influence of these properties.

We believe that gathering in a Special Issue a series of works dealing with these topics would be a great service for the researchers studying the flame retardancy of polymers.

Rodolphe Sonnier
Laurent Ferry
Guest Editors

Manuscript Submission Information

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Keywords

  • flame retardancy
  • flammability
  • thermophysical properties
  • optical properties
  • thermal conductivity
  • absorption in-depth
  • reflectivity
  • emissivity

Published Papers (9 papers)

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Open AccessArticle Characterization of Thermo-Physical Properties of EVA/ATH: Application to Gasification Experiments and Pyrolysis Modeling
Materials 2015, 8(11), 7837-7863; doi:10.3390/ma8115428
Received: 15 October 2015 / Revised: 6 November 2015 / Accepted: 11 November 2015 / Published: 20 November 2015
Cited by 3 | PDF Full-text (5769 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle Controlled Emissivity Coatings to Delay Ignition of Polyethylene
Materials 2015, 8(10), 6935-6949; doi:10.3390/ma8105349
Received: 9 June 2015 / Revised: 25 September 2015 / Accepted: 30 September 2015 / Published: 12 October 2015
Cited by 1 | PDF Full-text (6238 KB) | HTML Full-text | XML Full-text
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
Open AccessArticle Pyrolysis Model Development for a Multilayer Floor Covering
Materials 2015, 8(9), 6117-6153; doi:10.3390/ma8095295
Received: 29 July 2015 / Revised: 5 September 2015 / Accepted: 7 September 2015 / Published: 14 September 2015
Cited by 5 | PDF Full-text (8845 KB) | HTML Full-text | XML Full-text | 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
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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
Open AccessArticle Influence of Flame Retardants on the Melt Dripping Behaviour of Thermoplastic Polymers
Materials 2015, 8(9), 5621-5646; doi:10.3390/ma8095267
Received: 19 June 2015 / Revised: 14 August 2015 / Accepted: 20 August 2015 / Published: 27 August 2015
Cited by 7 | PDF Full-text (4823 KB) | HTML Full-text | XML Full-text | Supplementary Files
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
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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
Open AccessArticle On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials
Materials 2015, 8(8), 5398-5413; doi:10.3390/ma8085251
Received: 15 June 2015 / Revised: 21 July 2015 / Accepted: 17 August 2015 / Published: 21 August 2015
Cited by 4 | PDF Full-text (980 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle The Effects of Thermophysical Properties and Environmental Conditions on Fire Performance of Intumescent Coatings on Glass Fibre-Reinforced Epoxy Composites
Materials 2015, 8(8), 5216-5237; doi:10.3390/ma8085216
Received: 29 May 2015 / Revised: 21 July 2015 / Accepted: 28 July 2015 / Published: 11 August 2015
Cited by 4 | PDF Full-text (2780 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle Important Parameter Groups in Thermal Protection of Polymers
Materials 2015, 8(8), 4679-4698; doi:10.3390/ma8084679
Received: 18 June 2015 / Revised: 10 July 2015 / Accepted: 13 July 2015 / Published: 24 July 2015
PDF Full-text (797 KB) | HTML Full-text | XML Full-text
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
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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
Open AccessArticle Experimental and Numerical Study on Effect of Sample Orientation on Auto-Ignition and Piloted Ignition of Poly(methyl methacrylate)
Materials 2015, 8(7), 4004-4021; doi:10.3390/ma8074004
Received: 23 May 2015 / Revised: 21 June 2015 / Accepted: 29 June 2015 / Published: 2 July 2015
PDF Full-text (1420 KB) | HTML Full-text | XML Full-text
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

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Open AccessCorrection Correction: McKinnon M.B. and Stoliarov S.I. Pyrolysis Model Development for a Multilayer Floor Covering. Materials 2015, 8, 6117–6153
Materials 2015, 8(11), 7587-7588; doi:10.3390/ma8115402
Received: 6 November 2015 / Accepted: 6 November 2015 / Published: 11 November 2015
PDF Full-text (159 KB) | HTML Full-text | XML Full-text
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
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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
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