Rodolphe Sonnier

From a bio-based phosphorus-containing epoxy monomer to fully bio-based flame-retardant thermosets

In this work, phloroglucinol was used as a renewable resource to prepare an epoxy monomer and phosphorus containing reactive flame retardant (FR). These building blocks were reacted with diamines to obtain partly or fully bio-based flame retardant epoxy resins. It was highlighted that the glass transition temperature of the materials was tightly related to the functionality of the reactive monomers and the resulting crosslink density. Thermal stability and char yield of the thermosets seems to be mainly governed by the aromaticity of the monomers, the linking rate of the aromatic ring and the phosphorus content. Phosphorus FR are more efficient in intrinsically poorly charring matrices. It was evidenced that the flammability of bio-based epoxies can be monitored by two strategies: (i) choosing bio-based monomers with high charring ability and low combustion energy, (ii) incorporating bio-based phosphorus-containing reactive FR in the polymer network.

Finest nanocomposite films from carbon nanotube-loaded poly(methyl methacrylate) nanoparticles obtained by the Ouzo effect

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.

Fire behavior of halogen-free flame retardant electrical cables with the cone calorimeter

Fires involving electrical cables are one of the main hazards in Nuclear Power Plants (NPPs). Cables are complex assemblies including several polymeric parts (insulation, bedding, sheath) constituting fuel sources. This study provides an in-depth characterization of the fire behavior of two halogen-free flame retardant cables used in NPPs using the cone calorimeter. The influence of two key parameters, namely the external heat flux and the spacing between cables, on the cable fire characteristics is especially investigated. The prominent role of the outer sheath material on the ignition and the burning at early times was highlighted. A parameter of utmost importance called transition heat flux, was identified and depends on the composition and the structure of the cable. Below this heat flux, the decomposition is limited and concerns only the sheath. Above it, fire hazard is greatly enhanced because most often non-flame retarded insulation part contributes to heat release. The influence of spacing appears complex, and depends on the considered fire property.

Synthesis of biobased phosphate flame retardants

Abstract 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.

Synthesis of polyphosphorinanes Part II. Preparation, characterization and thermal properties of novel flame retardants

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.

Dynamic rheological studies and applicability of time–temperature superposition principle for PA12/SEBS-g-MA blends

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.

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

AbstractThe 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.

Incorporation of elastomer into poly(ether ether ketone) an attempt to improve the damping factor

The incorporation of an elastomer phase into a poly(ether ether ketone) (PEEK) matrix was carried out using two different processing methods (melt blending (MB) and dry blending) to improve the damping factor (tan δ) of the composite with a minimal change in the PEEK stiffness. A cross-linked fluoroelastomer (CFE) was carefully chosen according to its high glass transition temperature (T α), high thermal stability and high modulus. The blends were characterized by scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), modified Oberst test, flexural test and pyrolysis combustion flow calorimeter. According to SEM micrographs, an original well-dispersed PEEK-elastomer composite was obtained. The tan δ of the materials was evaluated using DMTA and modified Oberst test. Both techniques indicate that the incorporation of 5–20 wt% of CFE fine powders only slightly increased the tan δ of the material. Moreover, a decrease in flexural modulus and thermal stability of the blends was detected when there was an increase in the CFE content. Even if the properties are not yet significantly improved, it was well ascribed that the MB method was suitable to mix elastomer particles within a PEEK matrix. Poor interfacial adhesion has been identified as the main key parameter, which should be improved in further work.

Gaseous effluents from the combustion of nanocomposites in controlled-ventilation conditions

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.

Thermal degradation and flammability of polyamide 11 filled with nanoboehmite

Abstract The flame-retardant effect of rod-like nanoboehmite was evaluated in biobased polyamide 11. Thermal analysis reveals that hydrated nanofillers modify the degradation pathway of polyamide 11 turning from a two-step to a single-step mechanism. The polymer thermal stability is increased due to interactions between polar groups and filler surface hydroxyl groups. Despite this improved thermal stability, polyamide 11/nanoboehmite composites exhibit shorter times to ignition in cone calorimeter. The phenomenon was attributed to changes in thermoradiative properties leading to a faster heating of the polymer surface. The most significant flame-retardant action is a reduction in heat release rate that was related to a barrier effect while endothermic water release seems to play a minor role.