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International audience; The fire reaction of various types of flammable lightweight materials is investigated using a cone calorimeter. The influences of parameters such as sample density, sample mass, effective heat of combustion and heat flux on the mass loss after exposition are discussed. Interpretations of the hemp fibers’ tests results lead us to propose a phenomenological model able to calculate the peak of heat release rate (pHRR) of such thermally thin materials, with or without flame retardant. A database gathering the whole results of tests performed on a large set of materials including fibers, bio-resources panels, bio-based concretes and fabrics is used to validate the proposed model. Interestingly, the model is found to be relevant also for denser wood specimens. The model is based on the distinction of the contributions of the exposed top layer and the deeper layer to the combustion. Indeed, in such materials, the heat conduction is limited (either by the intrinsic properties of the material or by the formation of an insulating char) and therefore the pHRR only depends on a limited volume of materials directly absorbing the heat flux from the radiant cone. Accuracy and limitations of the model are discussed.

International audience; Plant products arouse great interest in many fields (construction, automotive, textiles, etc …).However, some of their characteristics as their flammability represent major disadvantagesfor some applications. Research is now being conducted in academia and industry to developeffective methods of functionalizing or modifying the surface of these fibers to improve theirperformance. In this respect, radiation-grafting, based on the use of ionizing radiation(gamma or e-beam), represents an interesting method compared to chemical or enzymaticmethods. This technique makes it possible to generate radicals on the fibers allowing thegrafting of molecules of interest, thus offering a large spectrum of possibilities for themodification of the fibers [1][2]. Two ways for grafting under ionizing conditions can beused (Figure 1), pre irradiation and mutual irradiation. In any case, many factors conditionthe success of grafting reactions. In particular, the structure and the composition of thesubstrate influence the nature of the active species formed, and therefore, the feasibility ofthe grafting reaction. Some techniques, such as Electronic Paramagnetic Resonance (EPR),helps us to better understand these parameters, which will be the subject of this presentation.

National audience; Récemment apparu dans le paysage agricole français, le Miscanthus x Giganteus suscite un intérêt croissant dans les milieux académiques et industriels. La productivité et les facilités associées à sa culture couplées aux avantages classiques des matériaux d’origine végétale le rendent attractif pour des applications dans les secteurs de l’automobile et du bâtiment. A l’instar des autres biomasses, son inflammabilité, son hydrophilie peuvent cependant représenter un frein à son usage. Pour y remédier, de nombreuses techniques de fonctionnalisation ont été mises au point, parmi lesquelles le radiogreffage se présente comme une option de choix. Cette méthode consiste à exposer un substrat à des rayonnements ionisants, y générant des radicaux et des groupes fonctionnels permettant le greffage de molécules d’intérêt, offrant alors un large spectre de possibilités pour la modification des biomasses [1][2]. Cependant, de nombreux facteurs relatifs aux conditions opératoires mais aussi inhérents au substrat (composition, structure…) conditionnent le succès du traitement [3]. Cette présentation vise à exposer les résultats obtenus dans une démarche de compréhension de ces derniers en faisant notamment usage de la spectroscopie par résonance paramagnétique électronique (RPE).

L’utilisation de ressources végétales dans la formulation des matériaux permet de réduire l’impact environnemental du secteur de la construction. De telles ressources restent sensibles au feu. Cette étude vise à développer un traitement ignifugeant adapté aux isolants thermiques à base de fibres de chanvre. Le but est de limiter les impacts sanitaires et environnementaux du traitement, tout en optimisant les performances techniques des produits traités. Un protocole de laboratoire est mis en place pour évaluer l’effet retardateur de flamme du traitement. Les fibres traitées avec des solutions commerciales ou des formulations spécifiques sont soumises à différents essais de caractérisation incluant des essais d’inflammation directe, des essais à la petite flamme, des analyses thermiques (ATD-TG) et des essais au calorimètre à cône. Les résultats obtenus permettent d’orienter la formulation d’un traitement mais mettent également en évidence la complémentarité de ces méthodes d’analyse. Le couplage des résultats permet également de proposer un ajustement de modèles prédictifs conduisant à l’estimation du classement de réaction au feu selon l’Euroclasse des matériaux testés., Academic Journal of Civil Engineering, Vol 40 No 2 (2022): Special Issue - NoMaD 2022

International audience; L’utilisation de ressources végétales dans la formulation des matériaux permet de réduire l’impact environnemental du secteur de la construction. De telles ressources restent sensibles au feu. Cette étude vise à développer un traitement ignifugeant adapté aux isolants thermiques à base de fibres de chanvre. Le but est de limiter les impacts sanitaires et environnementaux du traitement, tout en optimisant les performances techniques des produits traités. Un protocole de laboratoire est mis en place pour évaluer l’effet retardateur de flamme du traitement. Les fibres traitées avec des solutions commerciales ou des formulations spécifiques sont soumises à différents essais de caractérisation incluant des essais d’inflammation directe, des essais à la petite flamme, des analyses thermiques (ATD-TG) et des essais au calorimètre à cône. Les résultats obtenus permettent d’orienter la formulation d’un traitement mais mettent également en évidence la complémentarité de ces méthodes d’analyse. Le couplage des résultats permet également de proposer un ajustement de modèles prédictifs conduisant à l’estimation du classement de réaction au feu selon l’Euroclasse des matériaux testés.

L’introduction de ressources végétales dans la formulation des matériaux permet de réduire l’impact environnemental du secteur de la construction. Cette étude vise à développer un traitement ignifugeant adapté aux isolants thermiques à base de fibres de chanvre. Le but est de limiter les impacts énergétiques, sanitaires et environnementaux du traitement, tout en optimisant les performances techniques des produits traités. Un protocole de laboratoire est mis en place pour évaluer l’effet retardateur de flamme du traitement. Les fibres traitées avec des solutions commerciales ou des formulations spécifiques sont soumises à différents essais de caractérisation incluant des essais d’inflammation directe, des essais à la petite flamme, des analyses thermiques (ATD-TG) et des essais au calorimètre à cône. Les résultats obtenus permettent d’orienter la formulation d’un traitement mais mettent également en évidence la complémentarité de ses méthodes d’analyse. Le couplage des résultats permet également de proposer un ajustement de modèles prédictifs conduisant à l’estimation du classement de réaction au feu selon l’Euroclasse des matériaux testés., Academic Journal of Civil Engineering, Vol 40 No 1 (2022): Special Issue - RUGC 2022

Les câbles constituent une source importante de départ et de propagation de feux, c’est pourquoi ils doivent être ignifugés. Si leur comportement au feu est évalué après fabrication, la durabilité dans le temps du traitement ignifuge a jusqu’à présent été peu évaluée alors que ceux-ci doivent rester en service pendant plusieurs décennies tout en étant soumis à des environnements potentiellement agressifs. Ce manque de connaissances peut être particulièrement critique, par exemple dans le cas des centrales nucléaires dont la durée de vie va être prolongée au-delà de 40 ans 1 . Il a été montré que, selon sa nature et le type de vieillissement, le comportement au feu d’un matériau peut être dégradé, maintenu ou même parfois amélioré 2. Dans cette étude, une formulation commerciale pour un câble de nouvelle génération, à base de PE/EVA ignifugé par trihydroxyde d’aluminium, a été injectée sous forme de plaques. Ces plaques ont été soumises à différentes conditions de vieillissement (température, exposition aux UV et rayonnement gamma) dans le but d’évaluer leur comportement au feu à l’aide d’essais au cône calorimètre. Les résultats mettent en particulier en évidence une modification sensible et délétère du comportement au feu du matériau lorsqu’il a été soumis à des doses d’irradiation gamma pouvant être atteintes après plusieurs décennies d’exposition à un faible débit de rayonnements ionisants. Le matériau subit une forte déformation après ignition, due à la réticulation de la fraction polyéthylène sous l’effet du rayonnement gamma 3 . Dans un second temps, les câbles constitués de cette gaine seront évalués afin de vérifier que les phénomènes observés sur la gaine se produisent également sur les câbles.

Le bois est depuis toujours utilisé dans la construction. Cet usage prend un nouvel essor depuis quelques années grâce aux nombreux produits techniques innovants en bois. Ce matériau est de plus en plus apprécié offrant de nombreuses possibilités pour construire, surélever, rénover et s’agrandir. Cependant, les révisions successives des réglementations du bâtiment et de la construction ont accru les exigences pour que les matériaux satisfassent aux spécifications en ce qui concerne les faibles émissions de formaldéhyde et la résistance élevée à la propagation de la flamme. Ainsi, l'industrie des panneaux est confrontée à une demande croissante en panneaux ignifugés et à faible émission de formaldéhyde. Dans ce contexte, la disponibilité de retardateurs de flamme efficaces, non toxiques et/ou biosourcés est activement recherchée. Néanmoins, la capacité de l'industrie à répondre efficacement à cette demande croissante a été entravée par les limites de la disponibilité d'additifs adéquats. Il est donc clé de pouvoir proposer de nouveaux additifs pour répondre à ces besoins.

Textile technologies have been metamorphosed over the past two decades, shifting technologically from conventional to multifunctional textiles [1]. A multi-layered textile with long-standing flame retardancy and electrical conductivity was prepared via layer-by-layer (LbL) coating fabrication. A coating of polyethylenimine (PEI), ammonium polyphosphate (APP), and a composite containing poly(aniline-co-melamine) and montmorillonite (MMT) were consecutively applied, and the resulting multi-layered fabrics was systematically analyzed by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and thermogravimetric analysis (TGA). Flame retardancy analysis by pyrolysis-combustion flow calorimetry (PCFC) and a vertical burning test confirmed a significant fall in the heat release rate (HRR) by flax fabrics treatment. More interestingly, a very low peak of HRR (pHRR) of 15 W/g with respect to 234 W/g for untreated flax fabrics should be highlighted. Mechanistically, TGA measurements confirmed condensed phase flame retardancy, as reflected in a significant rise by 37% in the amount of residue of the treated fabrics compared to 19% for the untreated flax fabrics. The vertical burning test verified the formation of a fireproof multi-layered fabric. The conductivity of the flax fabric was in the range of 1-8×10-7 S/cm before burning, but surprisingly the fabrics remained conductive over 30 S. To give the product another dimension, a fully bio-based flame retradnat system using phytic acid amalgamated with a bio-phosphorus precursor was designed and applied on the flax fabric. The flame retardancy of the obtained samples was also investigated and compared with the last samples.

Adding a chemical function to a substrate is an efficient way to endow it higher performances. The only way of functionalizing natural fibres is by modifying their surface. Radiation grafting by the means of ionizing rays is a sustainable way to reach a high level of performances, without adding additives like initiators.A large range of molecules with unsaturated vinyl (double bond C=C) are now available and suitable for radiation grafting. According to the reactivity of the molecule, grafting can be induced by direct radiation (simultaneous grafting in presence of the substrate and of the molecule) or pre-irradiation (surface radicals of the substrate are turned into peroxides, owing to irradiation in the air, and thermally reactivated (80-100°C) at the moment of the grafting in presence of the molecule).Since 2012, the authors have developed an advanced and continuous experience with the radiation grafting of fire-retardant molecules on natural fibres.The grafting of natural fibres with repellent molecules is another project currently under development. These advancements and the suitable radiation conditions (dose, radiation pathway) as far as the grafting conditions (molecule, combination of molecules, concentration, grafting rate ...) to reach the related objectives will be presented.

International audience; Pre-irradiation method was used to modify flax fabrics by grafting phosphorus compouds to improve their flame retardancy. A phosphorus-based flame retardant (FR) dimethyl(methacryloxy)methyl phosphonate (MAPC1) was used as unsaturated grafting agent. The grafting process follows three main steps. First, flax fibers were irradiated under electron beam at a dose ranging between 5 and 100 kGy, then the irradiated fabrics were impregnated by dipping them into an aqueous solution containing the MAPC1 monomer; finally a washing step of the treated fibers allows to remove unreacted monomers units and the free oligomers and polymers chains which are not covalently bonded to the flax structure. Different parameters have been studied such as radiation dose, temperature and duration of the grafting reaction and monomer concentration. In particular, it has been observed that MAPC1 is grafted in a homogeneous way into the bulk of the elementary flax fibers leading to high phosphorus rate of around 2 wt% for a dose 10 kGy and up to 7 wt% for a dose 100 kGy. The presence of radicals on the flax fibers after irradiation has been confirmed by Electron Paramagnetic Resonance (EPR). Grafting efficiency was assessed by infrared spectroscopy (FTIR) and quantified using Inductively Coupled Plasma (ICP-AES). The location of the grafted phosphorus polymer chains was assessed by Scanning Electron Microscope coupled with Energy Dispersive X-ray spectrometer (SEM-EDX) using phosphorus mapping of modified fibers. The effect of phosphorus grafting on thermal properties and fire behavior of flax fibers was studied using thermogravimetric analysis and pyrolysis combustion flow calorimetry.

International audience; This work is focused on the functionalization of flax fibers aiming to improve their flame retardancy by grafting a phosphorus-based flame retardant (FR), dimethyl(methacryloxy) methyl phosphonate (MAPC1). The pre-irradiation method was used, and the grafting process follows three main steps namely: the irradiation of flax fibers, the impregnation of irradiated fibers in FR solution and finally a washing step to remove unreacted monomer units and free oligomers and polymers chains not covalently bonded to the flax structure. The presence of radicals on the flax fibers after irradiation was confirmed by Electron Paramagnetic Resonance (EPR). Grafting efficiency was assessed by infrared spectroscopy (FTIR) and quantified using Inductively Coupled Plasma (ICP-AES). The location of the grafted phosphorus polymer chains was assessed by Scanning Electron Microscope coupled with Energy Dispersive X-ray spectrometer (SEM-EDX) using phosphorus mapping of modified fibers. The effect of phosphorus grafting on thermal properties and fire behavior of flax fibers was studied using thermogravimetric analysis and pyrolysis combustion flow calorimetry. Different parameters were studied such as the radiation dose, the temperature and the duration of the grafting reaction and the monomer concentration. In particular, it was observed that MAPC1 was grafted in a homogeneous way into the bulk of the elementary flax fibers leading to high phosphorus rate of around 2 wt% for a dose 10 kGy and up to 7 wt% for a dose 100 kGy leading to high charring and low flammable fibers. The assessments are based on the measurement of density and thermal conductivity. The variation of compressive strength in function of the characteristics (mean particle length) of rice straw particle are assessed and discussed. The investigation covers also the porosity and density. Tests are also carried out on agricultural by-products with a view to highlight their chemical, physical and structural proprieties. The results show that the use of large particles with low water absorption capacity induce lighter concretes with the density between 339 and 505 kg/m3 and lead to a high compressive strength with a high mechanical deformability. Furthermore, it appears that an increase in the average length of rice straw particle lead to decrease of thermal conductivity of bio-based concretes. It varies from 0.062 to 0.085 W/(m.K).

International audience

International audience; Due to their chemical structure, conventional flame retardants are often toxic, barely biodegradable and consequently neither healthy nor environmentally friendly. Their use is therefore increasingly limited by regulations. For this reason, research on innovative flame retardants based on sustainable materials is the main focus of this work. Wheat starch, wheat protein, xylan and tannin were modified with phosphate salts in molten urea. The functionalization leads to the incorporation of phosphates (up to 48 wt.%) and nitrogen (up to 22 wt.%). The derivatives were applied on wood fibers and tested as flame retardants. The results indicate that these modified biopolymers can provide the same flame-retardant performances as commercial compounds currently used in the wood fiber industry. Besides, the flame retardancy smoldering effects may also be reduced compared to unmodified wood fibers depending on the used biopolymer. These results show that different biopolymers modified in phosphate/urea systems are a serious alternative to conventional flame retardants.

National audience

Dans un premier temps, la nature pétrographique et les propriétés physiques de deux terres à bâtir seront caractérisées (analyse granulométrique, densité spécifique, limite de liquidité et indice de plasticité). Les propriétés physiques de deux briques de terre crue (un adobe et une brique de terre compressée stabilisée à la chaux) fabriquées à partir de ces deux terres seront ensuite mesurées (masse volumique apparente, porosité, conductivité thermique, coefficient d’absorption d’eau, isotherme de sorption, comportement au feu). Les résultats obtenus montrent que les propriétés physiques qui sont le plus influencées par la nature de la terre utilisée sont la rétention d’eau et le comportement au feu., Academic Journal of Civil Engineering, Vol 38 No 1 (2020): Special Issue - RUGC 2020 Marrakech

International audience

International audience

International audience; De nouvelles réglementations pour la protection de la santé et de l’environnement comme les Euroclasses poussent les industriels de la câblerie à se renouveler. Ils se doivent d’intégrer ces normes tout en continuant à améliorer les propriétés mécaniques et électriques, ainsi que le comportement au feu et le vieillissement des câbles. A l’heure actuelle, les matériaux utilisés pour les gaines des câbles sont des mélanges de polymères chargés en hydroxyde d’aluminium (ATH) ou en polyphosphate d’ammonium (APP). Des taux de charges élevés sont nécessaires pour améliorer le comportement au feu, cependant ils impactent défavorablement la flexibilité de la gaine ou sa sensibilité à l’eau. L’approche menée dans le cadre du projet HAREDY vise à améliorer les performances au feu des matériaux et également à retarder leur vieillissement hygro- et hydrothermique.

International audience; This study reports the functionalization of natural fibers aiming to improve their flame retardancy. Flax fabrics were modified by pre-irradiation grafting method using electron beam radiation treatment. A phosphorus-based flame retardant (FR) dimethyl(methacryloxy)methyl phosphonate (MAPC1), was used as flame retardant grafting agent. The grafting process follows three main steps. Flax fibers were first irradiated at a dose ranging between 5 and 100 kGy and stored cold to preserve the radicals created over the long period before being immersed into an aqueous solution containing MAPC1 monomer. Finally, a washing step of the treated fibers allowed to remove the unreacted monomer units but also the free oligomers and polymers chains which were not covalently bonded to the flax structure. The presence of free radicals on the flax fibers after irradiation was confirmed by Electron Paramagnetic Resonance (EPR). Grafting efficiency was evidenced by infrared spectroscopy (FTIR) and quantified using Inductively Coupled Plasma Atomic Emision Spectroscopy (ICP-AES). The location of the grafted phosphorus polymer chains in the fibers structure was assessed by Scanning Electron Microscope coupled with Energy Dispersive X-ray spectrometer (SEM-EDX). The effect of phosphorus grafting on the thermal properties and fire behavior of flax fibers was studied using thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC) and a preliminary fire test. Different parameters were monitored such as radiation dose, monomer concentration, temperature and reaction duration on the grafting efficiency. In particular, it has been observed that MAPC1 was grafted in a homogeneous way into the bulk of the elementary flax fibers leading to high phosphorus content of around 2 wt% for a dose of 10 kGy and up to 7 wt% for a dose of 100 kGy.

International audience

International audience

International audience; Nowadays, natural fibres are considered as alternative bio-based reinforcements to synthetic fibres for composite applications. Indeed, natural fibres have many attractive advantages: renewability, biodegradability, good availability, low cost, low density, low abrasiveness, and they exhibit high specific stiffness and strength, in some cases as high as glass fibres, combined with interesting damping properties.Nevertheless, natural fibres also have some drawbacks as their flammability, low thermal stability, sensitivity to moisture and polar character lead to poor compatibility with hydrophobic polymer matrices. Therefore, modifications of natural fibres are required in order to target demanding technical and high performing applications.This Special Issue proposes to gather a series of articles dealing with the modification and control of annual plant fibres or wood properties for polymer composite applications. Indeed, composite properties can be controlled through various functionalization or impregnation treatments of plant fibres and wood, including chemical, enzymatic and physical treatments, such as ionizing radiations. Bulk and surface impregnation and grafting, coating, as well as modification of surface roughness, can be considered as strategies to enhance plant fibres, wood and resulting composites performances. Besides, relationships between specific biochemical and structural characteristics of plant fibres and wood and the efficiency of the modification and functionalization treatments are key issues (e.g., grafting regio-selectivity, interactions of functionalizing molecules with ligno-cellulosic substrates, …).The targeted properties could be flame retardancy, thermo-mechanical performances, improved resistance to water or other ageing conditions (non-exhaustive list). Modifications of plant fibres allowing their easier processing, or their incorporation into new performing polymer matrices, will also be considered.

International audience

International audience

International audience; Magnesium dihydroxide (MDH) was evaluated as char promoter into different polymers exhibiting various chemical structures. Char promotion was characterized using thermogravimetric analysis and pyrolysis‐combustion flow calorimetry. Gases released during pyrolysis were identified using pyrolysis coupled gas chromatography/mass spectrometry and thermogravimetric analysis coupled Fourier transform infrared spectroscopy. Relationships between the MDH effect (according to the char content and its thermal stability) and the chemical structure of the host polymers were identified. It was shown that MDH can be a good char promoter for aromatic polyesters such as polybutylene terephtalate and polyethylene terephtalate. Char promotion can be considered as one of the main mode‐of‐action of MDH at low or moderate filler content. An optimum was observed at approximately 20wt.% of MDH. Magnesium oxide was also studied as substitute to MDH to avoid hydrolysis phenomena due to the water release. But it was demonstrated that MDH was more efficient as a char promoter for polybutylene terephtalate than magnesium oxide.

International audience

International audience

International audience

International audience; The influence of environmental ageing on the reaction-to-fire of flame retarded polymers is reviewed. Six types of stimuli have been identified as the most relevant parameters inducing fire behavior modification: temperature, moisture, UV radiation, ionizing radiation, chemical solvent and physical stress. This review provides a state of the art and current comprehension about the effects of ageing on flame retardancy of polymers. Various physical and chemical phenomena lead to ageing and deterioration (or sometimes improvement) of the flame retardancy of polymers: release of additives (not only flame retardants) through thermal migration, solubilization, abrasion…, chemical degradation of the flame retardant system, chemical or physical modification of the polymer structure (chain scissions, crosslinking, diffusion of water…). Obviously, ageing effects strongly depend on the material and the ageing scenario considered. Solutions to maintain flame retardant efficiency in aggressive conditions are also presented.

Issu de : 13th International Conference of Polymers for Advanced Technologies, Hangzhou, PEOPLES R CHINA, JUN 25-28, 2015; International audience; Poly(dimethylsiloxane) (PDMS) filled with low contents of multiwall carbon nanotubes (MWCNT) was prepared using different ways to monitor the dispersion of MWCNT. The influence of the dispersion on thermal conductivity and transmittance was measured. High degree of transparence can be achieved with 0.02 phr of well dispersed MWCNT. Time-to-ignition (TTI) was also measured on 2- or 4-mm-thick specimens heated using radiative unidirectional source. Time-to-ignition was found to decrease with the incorporation of MWCNT because more heat is absorbed at the surface. Higher time-to-ignition was observed for partially translucent composites, due to different absorption in-depth profiles. It can be assumed that time-to-ignition can be controlled by the dispersion of MWCNT into the polymeric matrix.

International audience; Carbon nanotube-based poly(methyl methacrylate) and polyamide-6 nanocomposites have been investigated using various techniques within the framework of the NANOFEU project. Scanning transmission electron microscopy was used to characterize morphologies of composites, while fire properties were studied using cone calorimeter and pyrolysis combustion flow microcalorimeter. The study focused particularly on composition and microstructure of gaseous and aerosol products. Morphology of ultrafine particles released from the combustion of nanocomposites was studied using cascade impactor and atomic force microscopy. Fire behaviour has been interpreted in relation with the degradation mechanisms specifically induced by the presence of carbon nanotubes.

International audience; The thermal and fire properties of polystyrene (PS) flame retarded by a system composed of ammonium polyphosphate (APP) and wollastonite (W) were investigated by thermogravimetric analysis, pyrolysis-combustion flow calorimeter, pyrolysis gas chromatography mass spectrometry, cone calorimetry and epiradiator. The combustion residues were observed by scanning electron microscopy/energy dispersive X-ray spectroscopy and analyzed by X-ray diffraction. The combination of both additives enables increasing the thermal stability of PS while increasing simultaneously the high temperature residue. The peak of HRR was also significantly reduced while time to ignition varied depending on the composition. It was shown that the degradation pathway of PS was affected by the presence of the additives implying a reduction of the effective heat of combustion. In the condensed phase, APP decomposition promotes char formation and favors the reactivity between phosphorus and silicate. A layer composed of char, W and a mixture of calcium and silicon phosphate is formed at the sample surface during combustion. This layer is cohesive enough to limit the release of combustible gases to the gas phase. Moreover, the thermally stable protective layer reaches high temperature enabling the re-irradiation of a part of the incident heat flux. The flame retardancy of PS is thus enhanced.

International audience; Les stratégies d’ignifugation des fibres et textiles dépendent de leur nature (faible ou forte inflammabilité),des exigences réglementaires plus ou moins strictes selon le domaine d’application et de la durabilité du traitement recherchée. Des solutions satisfaisantes ont été mises au point dans les décennies précédentes,mais la prise en compte de nouvelles contraintes d’ordre environnemental avec une diminution des coûts de production pousse à la recherche de solutions innovantes, notamment pour substituer les retardateurs de flamme halogénés et ceux libérant du formaldéhyde lors de la combustion du matériau. Ainsi, le développement de retardateurs de flamme phosphorés, l’utilisation de nanoparticules ou la modification de surface par traitement plasma sont quelques voies actuellement explorées.

International audience

International audience; The flammability of various flame retarded formulations containing different hydrated mineral fillers and/or phosphorous compounds and/or carbon nanotubes has been investigated using both cone calorimeter and PCFC. A method was proposed to evaluate the barrier effect of the flame retardant additives. This method is based on the fact that PCFC is non sensitive to physical flame retardant effects while both chemical and physical phenomena have a great effect on cone calorimeter results. Therefore normalized pHRR values obtained with both techniques does not always show a good correlation. It was highlighted that the mismatch between both pHRR results was related to the formation of a protective layer during combustion. Protective layers have been evidenced independently by visual observations. Thus it is proposed that the magnitude of the deviation from a perfect correlation between cone calorimeter and PCFC pHRRs could be used to quantify the magnitude of barrier effect. While the results obtained from different fire tests are generally not correlated, such an approach based on the complementarity of different techniques appears more relevant despite of its empirical nature.

International audience; The influence of magnesium dihydroxide (MDH) nanoparticles on thermal degradation and fire behavior of poly(methyl methacrylate) (PMMA) has been investigated by thermogravimetric analysis (TGA), cone calorimeter, and pyrolysis-combustion flow calorimeter (PCFC) tests, respectively. MDH nanoparticles with either lamellar or fibrous shape have been synthesized via a sol-gel technique and characterized by transmission electron microscopy (TEM) and X-ray diffraction analysis. PMMA-MDH nanocomposites have been prepared by melt blending the recovered MDH nanoparticles within PMMA at different loadings (5, 10, and 20 wt% MDH). According to TGA results, the incorporation of lamellar or fibrous MDH nanoparticles into PMMA leads to a significant improvement in PMMA thermal stability, both under air and inert atmosphere. The results obtained by PCFC and cone calorimeter tests show an important decrease in the peak of heat release rate (pHRR) concomitant with charring during the combustion. Lamellar MDH nanoparticles were found to be more efficient than fibrous MDH nanoparticles.

International audience; In this study, polymer compounds consisting in a recycled polyolefin matrix (high or low density polyethylene (HDPE or LDPE)) and ground tyre rubber (GTR) powder are developed. The major problem in this two phase systems is the very poor interfacial adhesion between thermoplastic matrix and rubber filler, which impairs the mechanical properties of the compound. Two treatments have been tested to improve the adhesion and so the mechanical performances: GTR powder was oxidized either by reaction with potassium permanganate aqueous solution (0-20%wt of KMnO_4) or by irradiation (gamma-irradiation: 0-100 kGy). Oxidized GTR powders were then introduced into a HDPE matrix containing Maleic Anhydride grafted HDPE as a compatibilizing agent. While no significant improvement of mechanical properties was observed for the irradiated GTR powder, the KMnO_4 treatment lead to improved Young’s modulus and yield stress, but the adhesion mechanism involved was not clearly identified.; L’influence de l’incorporation de poudrettes de pneumatiques commerciales dans du polyéthylène (haute et basse densité) recyclé sur les propriétés mécaniques de mélanges PE/poudre a été étudiée. Les résultats des tests mettent en évidence la chute des performances en raison de l’absence d’adhésion matrice/particule. Deux traitements de comptabilisation ont donc été expérimentés. L’oxydation par irradiation gamma de la poudrette et son incorporation dans une matrice contenant une petite quantité de fonctions anhydride maléique n’a pas permis d’améliorer les propriétés mécaniques, bien que l’oxydation ait été effective. Un traitement par permanganate de potassium a donné au contraire des résultats intéressants, mais le mécanisme expliquant l’augmentation du module d’Young n’est pas encore élucidé.

En este artículo se analiza el comportamiento al fuego de siete maderas frondosas mejicanas. La finalidad es intentar determinar cuáles son los parámetros que ejercen influencia en el comportamiento al fuego de la madera. Uno de los factores que se considera clave es la densidad, ya que está relacionada con la velocidad de carbonización y por consiguiente esto afecta a las reacciones de pirólisis. Sin embargo, la densidad no es el único factor que influye en el comportamiento al fuego de la madera. En este trabajo se estudian siete frondosas diferentes y se analizan los resultados de los ensayos de reacción al fuego en relación a las propiedades físicoquímicas de la madera.