Search

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. Copyright © 2010 John Wiley & Sons, Ltd.

Results concerning γ-irradiation of polymer blends such as HDPE/ground tire rubber (GTR) and PP/HDPE are reported in this article with a special emphasis on the order of processing steps. Irradiation dose varied in the range 0–100 kGy. The two first polymers (HDPE and rubber) are preferentially crosslinked under γ irradiation while PP undergoes chain scission. Mechanical tests and differential scanning calorimetry (DSC) analysis show that the efficiency of the reactive compatibilization by γ irradiation depends greatly on the chronology of γ-irradiation and injection-molding steps. Electron spin resonance (ESR) results reveal that numerous radicals remain trapped in the materials after γ-irradiation even after a long time. Then the effect of irradiation on material properties is different if polymers are melted after irradiation or not. Crosslinking and chain scission are not affected in an equivalent way by the order of processing steps. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

International audience; This paper deals with the compatibilization between recycled HDPE matrix and ground tyre rubber powder, through a free radical mechanism, by adding a peroxide. Mechanical tests show competition between the crosslinking of HDPE and the formation of interfacial bonding. The addition of more than 1 %wt of peroxide results in a strong improvement of interfacial adhesion and elongation at break. The performance is also compared to that resulting from gamma irradiation of the same blends.In the second part of this article, experimental tests and simulation by finite elements analysis were performed and showed the non-possibility of obtaining a “thermoplastic elastomer” by blending and compatibilizing HDPE and ground tyre rubber powder, since perfect interfacial adhesion still results in decohesion between matrix and particles.

International audience; A new method is proposed to calculate the flammability of polymers from their chemical structure using a Van Krevelen approach. The model is inspired from a pioneering work of Lyon which assigns one flammability contribution to each chemical group. The flammability property of the whole polymer is the sum of the contributions of chemical groups constituting the polymer. Two intrinsic properties (namely heat release capacity and total heat release) measured using pyrolysis-combustion flow calorimeter are correctly predicted for almost one hundred polymers containing contributions of only 31 chemical groups. The contributions of these groups are compared and the consistency of these values is discussed. Finally some exceptions, such as, phosphorus-containing polymers, are noted.

International audience; A method to distinguish the mass loss rates corresponding to each of the two decomposition steps in binary blends is proposed. This method is suitable for cone calorimeter test and all other tests measuring continuously mass loss and heat release in an independent way. Heat release rate curves recalculated from the method well fit the experimental ones. Several systems including copolymers, polymers filled with inert or hydrated fillers and binary blends were studied. It appears that the decomposition of these materials is complex because the decomposition rate of one component influences the decomposition rate of the second one. These interactions depend on the materials, their content and also the external heat flux. Concerning binary blends, first results show the decomposition of the most thermally stable polymer is delayed because the temperature within the material is maintained close to the pyrolysis temperature of the least thermally stable polymer. Longer is the delay, higher is the decomposition rate of the most thermally stable polymer. In some cases, this polymer can decompose at higher rate (but later) than the least stable polymer.

International audience; Expanded polystyrene (EPS) foam has been successfully flame retarded by a water-based coating containing nanoparticles of boehmite and poly(vinyl alcohol) (PVOH) as char former. Boehmite enhances the charring of PVOH. The influence of suspension viscosity, coatings number, impregnation time and drying method was studied to monitor the amount of coating deposited and the coating thickness. The coating suspension is able to penetrate into the core of the foam. EPS without hexabromocyclododecane (HBCD) is upgraded from F to E rating according to the NF EN ISO 11925-2 standard when the penetration of coating suspension into the core is high enough, due to the formation of a char layer reinforced by nano-boehmites even if EPS does not shrink away from the flame.

A method to estimate the thermo-oxidative stability of chars is proposed using pyrolysis-combustion flow calorimetry. The temperature of char degradation is measured for different oxygen fractions (from 0.01 to 0.4, i.e. from 0 to 40%) into the pyrolyzer. Then the thermo-oxidative stability versus the oxygen fraction is modelled using a simple phenomenological equation. Two parameters have been calculated: the first one predicts the temperature of char degradation in “pure” oxygen and the second one corresponds to the sensitivity of the char degradation temperature to the oxygen fraction. These two parameters allow comparing the chars obtained from different materials after various pyrolysis procedures. Rough relationships between these two parameters and the elemental composition of char are identified. Phosphorus allows improving the thermo-oxidative stability of chars as expected but its effect is nonlinear. Lignocellulosic materials lead to chars with low thermal stability even when the phosphorus content is high. Finally, the obtained results show that the char elemental composition is not the only parameter influencing its thermo-oxidative stability.

Results concerning the influence of the modification of morphological and chemical characteristics of ground tyre rubber (GTR) powders on the mechanical properties of polyethylene (HDPE or LDPE)/GTR blends are given. In order to improve the interfacial adhesion between rubber particles and matrix, two oxidation treatments of the GTR powder by potassium permanganate (in solution) and γ-irradiation (in air) were performed. Then, the powder was incorporated in a HDPE matrix containing a small amount of maleic anhydride grafted polyethylene (MAgPE). The effect on the mechanical properties of the blends was studied. Since none of them was really effective, we conclude that oxidation cannot compensate for the lack of chemical reactivity of GTR powders.

An organophosphorus silica filler was generated in situ the molten PA66 copolymer (Cop-PA) during extrusion process without adding solvents. Nanocomposites synthesis is based on hydrolysis–condensation reactions of diethylphosphatoethyltriethoxysilane precursor (SiP). The thermal stability of Cop-PA/SiP nanocomposites and the major degradation products were studied by thermogravimetric analysis (TGA) and TGA coupled with Infrared spectrometry (TGA/FTIR). The Pyrolysis Combustion Flow Calorimeter (PCFC) and cone calorimeter were used to investigate the fire behaviour of the nanocomposites. Results showed a decrease by more than 50% of the peak of heat release rate (PHRR) and the formation of an expanded char layer with the addition of only 0.91wt% of silicon and 0.96wt% of phosphorus by this original route of fillers dispersion.

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 behaviour modification: temperature, moisture, UV radiation, ionizing radiation, chemical solvent and physical stress. This review provides a state of the art and current comprehension of 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, etc., chemical degradation of the flame-retardant system, and chemical or physical modification of the polymer structure (chain scission, crosslinking, diffusion of water, etc.). 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. © 2014 Society of Chemical Industry

In the present work, γ irradiation is used for the in situ compatibilisation of blends of recycled high density polyethylene (rHDPE) and ground tyre rubber (GTR) powder. The expected compatibilisation mechanism involves the formation of free radicals, leading to chain scission within rubber particles, crosslinking of polyethylene matrix and co-crosslinking between the two blend components at the interface. While uncompatibilised rHDPE/GTR blends show poor mechanical properties, especially for elongation at break and Charpy impact strength, irradiation leads to a significant increase of these mechanical performances. Such behaviour is attributed to the development of an adhesion between GTR particles and the surrounding thermoplastic matrix. This conclusion is supported by in situ scanning electron microscopy observations during microtensile tests, showing strong elongation of GTR particles upon deformation of irradiated blends.

International audience; The viscoelastic behaviour of PA12/SEBS-g-MA blends was studied. Time sweep, amplitude sweep, and frequency sweep tests were analysed by the use of parallel-plate rheometer. Time sweep test shows time-independent viscoelastic behaviour of the polymer and blends during the entire duration of test. The critical shear strain was higher for PA12 as compared to that of SEBS-g-MA and the blends in amplitude sweep test. However, the plateau modulus was higher for SEBS-g-MA as compared to PA12. The complex viscosity, dynamic storage, and loss moduli of PA12 increased with the addition of SEBS-g-MA as a consequence of phase interaction between them. The influence of phase morphology of blend composition on their rheological properties was also examined. The blend showed a transformation from liquid-like to solid-like behaviour. The decrease in viscosity for PA12 and blends was observed with increasing temperature. The van Gurp plots was successfully used to validate time-temperature superposition principle (TTS) for PA12, SEBS-g-MA and blend compositions. PA12 holds TTS with a horizontal shift factor that fits Arrhenius equation. Whereas TTS fails for SEBS-g-MA and the blends studied because of different temperature-sensitive response and microstructural changes of melt during shear application.

Authors would like to thank Christine LUCAS for help in solid state NMR experiments, C2P2 (Chemistry, Catalysis, Polymer & Processes), UMR 5265 - University of Lyon 1.; International audience; A new silicophosphorylated filler was generated in situ in a molten PA66 copolymer during extrusion process with the aim to improve the fire behavior of the matrix. The filler was obtained in one step via hydrolysis–condensation reactions of SiDOPO precursor (DOPO, 9,10-dihydro-9-oxa-10-phosphaphenanthrene). The synthesis of the precursor is reported and characterized by NMR. A 29Si NMR study of SiDOPO hydrolysis–condensation reactions in N-methylacetamide (NMA) solvent was also conducted. Thermal stability of Cop-PA/SiDOPO composite and the major degradation products were studied by thermogravimetric analysis coupled with Infrared spectrometry (TGA/FTIR). The Pyrolysis Combustion Flow Calorimeter (PCFC) and cone calorimeter were used to investigate the fire behavior of the composite. Results show that the nanocomposite exhibits a little earlier ignition but with a decrease around 33% of the peak of heat release rate (PHRR). The presence at low concentration of silicon (0.65 wt.%) and phosphorus (0.75 wt.%) promotes the formation of an expanded char layer that acts as a barrier. A reduction of about 18% in effective heat of combustion (EHC) values suggests an additional flame inhibition effect of phosphorus in the gas phase.

In this study, expanded graphite (EG) was investigated as flame retardant for epoxy resin based on DGEBA. Various amounts of EG (up to 50 wt%) were incorporated into the epoxy and the composites were studied using X-ray diffractometer, scanning electronic microscopy, cone calorimeter, pyrolysis-combustion flow calorimeter, thermogravimetric analysis, instrumented epiradiator and laser-flash method. Quite unexpectedly, EG leads to a significant increase in pHRR in cone calorimeter tests. Nevertheless, EG also allows delaying strongly the time-to-ignition. Such behavior was assigned mainly to the increase in thermal diffusivity which allows transferring heat faster from the surface to the bulk.

International audience; Two phosphorus-based molecules were grafted onto flax fibers through electron beam irradiation in order to impart flame retardancy to flax fabrics. Fabrics were impregnated by dipping them into a solution containing a phosphonated monomer: dimethyl(methacryloxy)methyl phosphonate (MAPC1) or dimethylvinyl phosphonate (MVP). Then fabrics were irradiated at a dose ranging between 10 and 100 kGy. The grafting efficiency was found to be dependent on the molecule concentration in the impregnation solution, on the radiation dose and on the nature of the monomer. In particular, it has been observed that MAPC1 is grafted only onto the surface while MVP is also grafted into the bulk leading to high phosphorus content (4 wt%). Flame retardancy of the modified flax fibers, fabrics and polyester thermoset composites containing these fabrics were also investigated. High phosphorus content allows fabrics to achieve self-extinguishing behavior. The flammability of composites in cone calorimeter test is also reduced, even if the thermoset is not flame retarded itself.

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.

International audience; Surface modification of various silicas by phosphorous agents was carried out with the aim to use these particles as flame retardant additive in a polypropylene matrice (PP) at low content (10 wt%). Thermal and flammability properties of PP/modified silica (PP-Tm-10%, PP-Zm-10%) were studied using TGA, PCFC and cone calorimeter and compared to those conferred by pure silica (PP-T-10%, PP-Z-10%). Quite surprisingly the untreated fillers induce the most significant reduction of peak of Heat Release Rate (50% decrease) while the surface modification by phosphorous agents does not lead to the expected effect on the fire behavior of PP composite. This phenomenon was related to the morphology and rheological behavior of the various PP composites. Indeed, the higher the storage modulus at low frequencies is, the better the fire behavior is, because of the induced barrier effect. Moreover, the addition of non modified silicas leads to a decrease of 10 s of the TTI. This phenomenon was related to the formation of bubbles after the PP melting during cone calorimeter test.

International audience; The thermal behaviour and crystallization kinetics of PA12/SEBS-g-MA blends were investigated under non-isothermal and isothermal conditions using thermogravimetric analysis and differential scanning calorimetry, respectively. The macrokinetic model given by Avrami was used to analyse both the non-isothermal and isothermal crystallization kinetics of the blends. The value of the Avrami exponent during non-isothermal crystallization predicted that pure PA12 and PA12/SEBS-g-MA blends show spherulitic growth with random nucleation of crystal structures as the n-values lie between 3 and 4. The slight nucleating effect of SEBS-g-MA was showed by nucleating activity calculated by the Dobreva and Gutzowa method.

We present a new and original approach to prepare flame retardants (FR) compounds. The strategy adopted consists first in synthesizing new reactive phosphorus-containing oligomers and then to chemically graft them to an epoxy network. These reactive FR compounds are synthesized by radical chain transfer copolymerization of dimethoxy-phosphorylmethyl methacrylate (MAPC1) with glycidyl methacrylate (MAGLY). Reactivity ratios were determined rMAPC1 = 0.78 and rMAGLY = 1.28 at 80 °C. The molecular weight of all the (co)oligomers was calculated by steric exclusion chromatography between 1000 and 3000 g mol−1. The synthesized FR were incorporated into an epoxy matrix as reactive binders. Then these formulations were cured at high temperature and the cross-linking densities were determined by DSC. The thermal properties and burning behaviors of cured epoxy resins were investigated. Thermogravimetric analysis showed a small decrease in thermal stability accompanied by a 50% increase in char yield. Pyrolysis combustion flow calorimetry (PCFC) was also used to evaluate the flammability of the modified epoxy resin. A significant decrease in peak of heat release rate (pHRR) and total heat release (THR) was observed. Indeed, with 3%wP, the THR was reduced by 25% and the maximal heat release rate by 60% compared to the reference. These results demonstrate the good flame retardant properties of reactive oligomers in epoxy matrix.

International audience; The controlled dispersion of Stöber silica nanoparticles (SiNPs) at the interface of a PS/PA6 (80/20 wt%) blend was achieved by means of surface modifications using 3-methacryloxypropyltrimethoxysilane (MPS). The final localization of SiNPs in the blend was predicted using wetting parameter calculation and confirmed by scanning electronic microscopy (SEM) observations. Stability of blends during annealing was evaluated qualitatively by laser diffraction particle size analyzer. Morphologies of the blends in the molten state were observed using optical microscopy. Flammability of blends was investigated using pyrolysis-combustion flow calorimeter (PCFC). Results showed that both microstructure stability during annealing and thermal degradation of the blend, were improved when MPS-modified SiNPs are located at the interface. SEM pictures revealed that the MPS-modified SiNPs form a solid barrier between PS and PA6 phases which inhibits coalescence process and modifies the thermal degradation mechanisms.

International audience; Flame retardancy of EVA copolymers using three new synthesized and two commercial hydrated mineral aluminum-based fillers having different aspect ratio was studied. It was shown that the peak of heat release rate (pHRR) in cone calorimeter test significantly decreased in presence of lamellar-shaped pseudoboehmites compared to that observed in presence of aluminum trihydroxyde and boehmite. On the opposite, thermogravimetric analysis (TGA) and Pyrolysis Combustion Flow Calorimeter analysis (PCFC) did not show any significant modification between the five formulations indicating that the pHRR decrease is related to barrier effect and not to endothermic effect or to improvement of thermal stability. No relationship was found between the pHRR decrease and the melt viscosity. ESEM and EDX analyses have confirmed that the efficiency of the barrier effect in presence of the two lamellar pseudoboehmites is assigned to migration phenomena of particles which led to the quick formation of a homogeneous and cohesive insulating layer.

International audience; The flame retardant effect of ultrafine kaolinite in Ethylene Vinyl Acetate copolymer (EVA) was studied and compared to that conferred by aluminum trihydrate (ATH). The thermal degradation and flammability of EVA composites were evaluated up to 60 wt% filler loading. Thermogravimetric (TG) and cone calorimeter analyses showed a higher decomposition temperature range and an improved FR performance for EVA/kaolinite composites in comparison to EVA/ATH composites. For a loading of 35 wt%, the peak of heat release rate (pHRR) of EVA/kaolinite was reduced by 55% compared to EVA/ATH. Moreover, we observed that kaolinite leads to a significant intumescent behavior during cone calorimeter tests. Finally, the rheology in the molten state of the different samples was studied and viscosity seems to play an important role on the fire retardancy of EVA/kaolinite composites.

International audience; The present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.

International audience; This paper investigates the effects of cellulose, hemicellulose and lignin on the pyrolysis and combustion of several natural fibers (cotton linter, flax, hemp, sugar cane, bamboo and coir). Different parameters have been selected to study the relations between chemical composition, pyrolysis and combustion: char yield (Res), effective heat of combustion (EHC), activation energy of combustion (Ea) and CO/CO2 ratio during cone calorimeter test. A correlation was found between these parameters and the lignin content in a large range of composition. The natural fibers with high content of lignin exhibit high char yield, high EHC, high Ea and low CO/CO2 ratio. However, a particular behavior was observed at low lignin/cellulose ratio. The presence of a low content of lignin with a high content of cellulose affects the degradation pathway of the latter and leads to charring and to incomplete combustion of these fibers, limiting their contribution to the heat evolved during burning.

In this chapter the influence of phosphorus incorporated through a reactive approach on the flame retardancy of polymers is reviewed. Phosphorus modifies the degradation pathway of the polymer and hence its thermal stability and charring. Its activity in the vapor phase would be also an additional mode of action. The influence of the chemical environment on the efficiency of phosphorus as flame retardant is also discussed.

An approach to prepare some biobased flame retardant (FR) compounds is presented. The adopted strategy consists in functionalizing an aromatic biobased phenolic compound, the phloroglucinol, with different phosphate groups in order to promote a charring effect. Different chlorophosphates were grafted onto phloroglucinol hydroxy groups and the functionalization of the hydroxy groups was quantitative. The synthesized biobased FR were incorporated into an epoxy matrix as additive to estimate their flame retardant properties. The influence of different parameters was studied such as the phosphorus content of the thermoset or the nature of the R group of the used phosphate P-O-R. MEB/EDX observations proved the influence of this R group on the compatibility between the FR and the matrix and its importance to obtain homogeneous thermoset. Thermogravimetric analyses of the phosphorus-containing thermosets showed a small decrease in thermal stability accompanied by a char yield almost tripled for a 3 %wP-containing thermoset compared to that of the thermoset without any FR. Pyrolysis combustion flow calorimetry was also used to evaluate the flammability of the modified epoxy thermoset. A significant decrease in peak of heat release rate and total heat released was observed compared to thermoset without FR. These results demonstrate the good flame retardant properties of these biobased phosphates in an epoxy matrix. In addition these results show the potential of the biobased phenolic compounds as raw material for flame retardants syntheses.

International audience; The flame retardancy of silicone composites containing calcium- and aluminum-based fillers has been investigated using several methods including cone calorimeter, Pyrolysis Combustion Flow Calorimeter (PCFC), thermogravimetric analysis and pyrolysis-gas chromatography-mass spectrometry analysis (Py-GC/MS). The fire reaction of precipitated calcium carbonate, calcite, calcium hydroxide, aluminum trihydrate, boehmite and alumina-based composites was correlated mainly with their thermal stability, while for mica and wollastonite-based composites, a barrier effect was also evidenced. The endothermic effect was not established as an efficient flame retardancy mechanism for the silicone composites containing hydrated fillers. Mica composite exhibited the best flame retardancy, in terms of depressed HRR, among all investigated formulations. Finally, a unique behavior was observed during the cone calorimeter test of calcium hydroxide-based composite, which co-crystallization with silica occurs exclusively at high heat flux.

International audience; Nanocomposites of polypropylene/polyamide 6 blends based on three different nanoclays: thermal stability and flame retardancy Summary-The influence of various layered silicates: sepiolite (needle-like structure), halloysite (nanotube structure) or organomodified montmorillonite (lamellar structure) in combination with phosphorous flame retardants [ammonium polyphosphate (APP) and aluminum diethylphos-phinate (OP)] on the properties and morphologies of compatibilized PP/PA 6 blends has been investigated. Thermal degradation and fire retardancy of these blends were explored using TGA, cone calorimeter, pyrolysis flow combustion calorimeter (PCFC). Morphology of nanocomposites and residues as well of the chemical structure formed after cone calorimeter tests were investigated. The sepiolite/APP composition led to the better fire performance through the formation of a large amount of charred and expanded residue reinforced by the sepiolite fibres. The better com-pactness of this residue than that of the montmorillonite/APP one enables to account for the interest of sepiolite, whereas montmorillonite exerts the better fire retardant role, alone in the polymer blend. Keywords: mineral filler, nanocomposite, halloysite, sepiolite, flame retardancy.; Streszczenie-Badano wp³yw ró¿nych warstwowych krzemianów: sepiolitu (struktura iglasta), haloizytu (struktura nanorurek) i organicznie modyfikowanego montmorylonitu (struktura p³yt-kowa), u¿ytych w uk³adzie z fosforowymi uniepalniaczami [poli(fosforanem amonu) (APP) lub dietylofosfin¹ glinu (OP)] na w³aoeciwooeci termiczne i ognioodpornooeae kompatybilizowanej mie-szaniny polimerów PP/PA 6. Degradacjê termiczn¹ oraz odpornooeae na ogieñ oceniano metod¹ TGA, za pomoc¹ kalorymetru sto¿kowego a tak¿e mikrokalorymetru pirolizy i spalania (PCFC). Morfologiê nanokompozytów oraz strukturê powsta³ej pozosta³ooeci po testach kalorymetrycz-nych badano za pomoc¹ skaningowej mikroskopii elektronowej (SEM). Zastosowanie uk³adu se-piolit/APP prowadzi do utworzenia na powierzchni próbki najwiêkszej ilooeci barierowej, zwêglo-nej pozosta³ooeci, dodatkowo wzmocnionej w³óknami sepiolitowymi, co umo¿liwia najlepsz¹ ochronê przed ogniem otrzymanego nanokompozytu. Wiêksza spoistooeae tej pozosta³ooeci ni¿ uzy-skanej w przypadku stosowania uk³adu montmorylonit/APP sk³ania do wiêkszego zainteresowa-nia glink¹ sepiolitow¹, mimo i¿ sam montmorylonit, u¿yty jako nape³niacz PP/PA 6 jest skutecz-niejszym oerodkiem uniepalniaj¹cym. S³owa kluczowe: nape³niacz mineralny, nanokompozyt, haloizyt, sepiolit, opóŸniacz palenia.

International audience; The combustion efficiency of various polymeric materials was studied using a pyrolysis–combustion flow calorimeter (PCFC). Decreasing the combustion temperature in a PCFC leads to partial combustion and lower heat release rates. Combustion efficiency versus combustion temperature was modeled using a phenomenological equation and model parameters were related to the chemical structures of eight pure polymers. The flame inhibition effect was evaluated for two classical approaches in flame retardancy by plotting the combustion efficiency versus the combustion temperature. In the first one (the reactive approach), polystyrenes with different chemical groups substituted on the aromatic ring were studied. In the second one (the additive approach), three well-known flame retardants were incorporated into an ABS matrix: ammonium polyphosphate, tetrabromobisphenol A (TBBA), and a TBBA/antimony trioxide system. Results confirm the flame inhibition effect of halogenated compounds in both approaches. Finally, a correlation between peaks of heat release rate (pHRR) in a cone calorimeter and in a PCFC was attempted. Predicting pHRR in a cone calorimeter using a PCFC appears possible when no barrier effect is expected, if PCFC tests are carried out at a precise combustion temperature, for which the combustion efficiencies in both tests are the same.

Transparent polycarbonate nanocomposites with improved fire behavior were prepared by incorporation of polyhedral oligomeric silsesquioxane (POSS) and resorcinol bis (diphenyl phosphate) (RDP) via melt blending. Flame retardancy performance was characterized using thermogravimetric analysis, pyrolysis combustion flow calorimeter and cone calorimeter. Simultaneous presence of RDP and POSS led to the decrease of the degradation rate and the increase of char residue due to the reaction of the additives with the decomposing polymer. This results in a significant reduction of flammability of polycarbonate. In cone calorimeter, the heat release rate as well as the smoke production rate were shown to strongly decrease due to a condensed phase mechanism that favored the formation of a cohesive char layer. Transparency evaluation was performed in both physical and psychophysical spaces. The two approaches give various assessment of transparency. Considering the perceived optical properties, it could be concluded that flame retarded PC is translucent rather than transparent.

International audience; Modified kaolinite poly(methyl methacrylate) nanocomposites were prepared using successively in situ polymerization and melt blending methods. Pristine kaolinite (Kaol) was intercalated using two organic molecules dimethyl sulfoxide (DMSO) and dodecylamine. This treated kaolinite (TKaol) was exfoliated via in situ polymerization of MMA. The prepared blends were extruded with a commercially available PMMA and then injection molded. The thermal degradation and flammability of TKaol PMMA nanocomposites was compared to pure PMMA and also to PMMA nanocomposites filled with untreated Kaol. Results showed the influence of Kaol morphology on fire behavior of these nanocomposites. The use of exfoliated Kaol allowed a better thermal stability to be achieved and the decrease of peak heat release rate (PHRR) as revealed by the cone calorimeter tests. Moreover, TKaol PMMA nanocomposite enabled to maintain time to ignition close to that of PMMA while it was largely reduced with PMMA nanocomposites filled with untreated Kaol. Finally, exfoliated Kaol led to an efficient barrier effect due to the formation of a cohesive residue as highlighted by its mechanical strength.

The thermal and fire-resistance properties of the ternary system ammonium polyphosphate/melamine polyphosphate/titanium dioxide (APP/MPP/TiO 2 ) was studied in poly(methyl methacrylate) (PMMA). PMMA-7.5%APP/7.5%TiO 2 showed an interesting thermal stability and synergy effects on the peak of heat released rate (pHRR). Mechanisms were investigated following the analysis of residues and gas phase. Residues were analyzed by Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM). Gases emitted during degradation were analyzed by Pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS). Comparison between cone calorimetry and pyrolysis–combustion flow calorimetry (PCFC) tests was a helpful tool for determining whether fire-retardancy mainly occurred by a physical or chemical pathway and for explaining the obtained results.

Polycarbonate/Poly(butylene terephthalate) (PC/PBT) blends are used in various industrial sectors, particularly in the cable industry. In this work, the fire behavior of PC/PBT blends was studied for the entire range of blend composition to investigate the relation between fire properties and blend morphology. The morphology of the binary blends used presents a phase inversion point for 25–30 wt % PBT. Various tests have been performed to characterize the fire behavior [limiting oxygen index (LOI), epiradiator test, cone calorimeter, and pyrolysis combustion flow calorimeter (PCFC)]. A change in fire behavior has been observed when the PBT content increases from 20 to 30 wt %, corresponding to the phase inversion, from a continuous rich-PC phase to a continuous rich-PBT phase. Consequently, it can be suggested that the control of the morphology of binary polymer blends is crucial to improve their fire properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

A comparison of alumina (Al2O3) and boehmite (AlOOH) in (ammonium polyphosphate/melamine polyphosphate/metal oxide) ternary system was performed in poly(methyl methacrylate) on thermal and fire-resistance properties. A Design of Experiments (DoE) was then done for highlighting the best formulation out of both ternary systems. Laser flash analysis and scanning electron microscopy helped to explain some of the observations made by DoE. Mechanisms in both ternary systems during degradation also were investigated and modes of action could be presented based on pyrolysis-combustion flow calorimetry, Raman spectroscopy and X-ray diffraction. Copyright © 2011 John Wiley & Sons, Ltd.

International audience; Composite materials are more and more used every day. In order to further enhance their attractive mechanical and physico chemical performances, the last generation of these materials largely makes use of nanomaterials. Various nanofillers are eligible for such a purpose, the best ones depending on the associated matrices. One favorite field of application of these nanomaterials is fire retardancy and fire behavior of nanocomposites. In the context of the ANR research project NanoFeu, various technical analyses have been performed [1]. One focuses on the characterization of the dispersion of nanofillers in the matrix; another deals with the characterization of the fire behavior of samples including the study of the composition of the gaseous effluents, the characterization of the emitted soot [2]. A third part of the work focused on molecular modeling of observed phenomena within the matrices. This paper focuses mainly on the combustion of nanocomposite samples under various ventilation conditions. Tests have been performed with the Fire Propagation Apparatus (FPA). Samples are based on poly(methyl methacrylate); various nanofillers were used: carbon nanotubes, alumina and silica. Efficiency of fillers is compared to the classical ammonium polyphosphate in equal proportions. During testing, the ventilation-controlled conditions were obtained by adjusting the combustion air flow rate entering the apparatus. Gaseous effluents were analyzed by Fourier Transform Infra-Red spectrometer. Fire behavior is characterized in terms of fire parameters and chemical composition of gaseous effluents. The influence of ventilation conditions is especially significant in terms of amount of gases released: much more important production of specific gases is generally observed in case of under ventilation regime as compared to the well ventilated case.

International audience; We report here the investigation of new flame retardant compounds for textiles, obtained by radical polymerization of allyloxydioxaphosphorinanes. These monomers were first synthesized by a transesterification reaction. A deep NMR study of such compounds revealed the existence of diastereoisomers Z and E. Radical polymerizations of allyloxydioxaphosphorinanes in the presence of a chain transfer agent, i.e. dimethylhydrogenophosphonate, led to oligomers of rather low molecular weights and especially adducts with DP 1 and 2. It was demonstrated that radical polymerization of allyloxydioxaphosphorinanes with P-R (R being alkyl or aryl) does afford only linear oligomers instead of hyperbranched polymers when R is hydrogen. The thermogravimetric analyses of the oligomers showed a good thermal stability and a high content of char residue (more than 16 wt%). The flame retardant properties were also evaluated by microcalorimeter tests and revealed an efficient behavior especially in the condensed phase, comparatively to Antiblaze 19, the flame retardant commercial product for polyester textile.

Composite particles, i.e. PMMA nanoparticles trapping one to a few nanotubes in their core, were prepared by a derivative process of the solvent shifting technique, also called the “Ouzo effect”. Particles were converted by simple annealing into nanocomposite films, the thermal resistance of which was evidenced by microcalorimetry and thermogravimetry.

In order to protect our environment, toxic compounds have to be replaced to meet the new regulations as well as industrial standards. Therefore, to be environmental friendly, some solutions have to be found in terms of fire safety, since halogenated compounds are still used in fire retardant systems. The way studied to solve this problem was to add silica fillers modified by phosphorous or nitrogen agents into two polymer matrices (polypropylene and polybutylene terephthalate). Two different techniques were used to modify the silica surface: the first by grafting and the second by impregnation. Only 10% by weight of untreated or modified fillers was introduced into the polymers thanks to extrusion process. Morphology studies, rheological and fire behaviors as well as thermogravimetric analyses were performed on composites and relationship between those properties have been established. In the case of polypropylene, the untreated fillers induce the most significant reduction of peak of Heat Release Rate while the surface modification by phosphorous agents does not lead to the expected effect on the fire behavior of PP composite. The origin of this phenomenon was deeply studied and was related to the difference of morphology and rheological behavior between the several PP composites. Concerning polybutylene terephthalate, the best fire performances were obtained for composites containing phosphorous modified silica. Given these results, relationships between the type of flame-retardant compound, the viscoelasticity, the formation of a fire protective layer and the improvement of fire behavior has been identified, Dans un contexte de lutte contre la dégradation de notre environnement, les lois et règlementations issues du Grenelle de l'environnement, obligent de trouver des solutions permettant de répondre à des normes tout en remplaçant des composés nocifs. Dans ce souci de respect de l'environnement, certains changements doivent s'opérer dans le domaine de la sécurité contre les incendies, puisqu'actuellement, les systèmes retardateurs de flammes contiennent des composés halogénés. Pour répondre à cette problématique, l'approche choisie a été d'introduire, des composés phosphorés et/ou azotés préalablement greffés ou imprégnés sur de la silice dans différentes matrices polymères. Les composites ont alors été réalisés à l'aide du procédé d'extrusion en introduisant, au sein d'un polypropylène ou d'un polybutylène téréphtalate, un faible taux de charges modifiées ou non, à savoir 10% en masse. Les études morphologique, rhéologique, thermogravimétrique mais également du comportement au feu des composites ont été réalisées et des relations entre toutes ces propriétés ont pu être établies. Dans le cas du polypropylène, l'ajout de silice non traitée a globalement entrainé un meilleur comportement au feu que l'ajout de silices modifiées, ce qui a été expliqué par des différences morphologiques et rhéologiques. Pour le polybutylène téréphatalate, les meilleures propriétés ont été observées lors de l'ajout de silices modifiées par les différents composés phosphorés. Grâce à ces résultats des liens étroits entre type de composé ignifugeant, viscoélasticité, formation d'une couche barrière protectrice et amélioration du comportement au feu ont été mis en évidence