Fabienne Samyn

Characterization and Reaction to Fire of Polymer Nanocomposites with and without Conventional Flame Retardants

In this work, the reaction to fire of polymer nanocomposites (thermoplastic polyurethane, polylactide and polyamide-6) containing different nanofillers (organoclay, polyhedral silsesquioxanes or POSS and carbon nanotube) is investigated. When high level of nanodispersion is achieved (shown by transmission electron microscopy (TEM)), they exhibit good flame retardancy in specific scenarii (high heat flux), but fail to flammability tests (LOI, UL-94). The mechanism of protection is the formation of mineral layer associated to char promotion but the protective coating is not efficient enough to provide the highest standard of protection. It is shown that this technology gives the best results combined with conventional flame retardants and leads to synergistic effects. The aspects of nanodispersion of the filler with the flame retardant are also fully commented in the paper using TEM and electron microprobe.

Fire behaviour of carbon fibre epoxy composite for aircraft: Novel test bench and experimental study

A versatile fire test has been developed with a complete set of instrumentation to investigate the fire behaviour of carbon fibre epoxy composite designed for aircraft. During a single test, both condensed and gas phases can be simultaneously studied measuring the temperature profile and the mass loss and studying the nature and quantity of volatile gaseous species. This novel test bench is compliant with two aeronautical certification fire tests: ISO2685:1998(E) and FAR25.856(b):2003. Titanium coupons have been first submitted to fire to validate the testing method. Composite coupons have been evaluated to examine completely their fire behaviour. To go further in the investigation, post-fire analyses have been performed using X-ray microtomographic images of coupons exposed to fire. Thus, the phenomena identified during the test are the apparition of cracks in the virgin material, the thermal degradation, the migration of evolved gases through the material up to both side and the thermal delamination.

Mapping the multimodal action of melamine-poly(aluminium phosphate) in the flame retardancy of polyamide 66

A higher analogue in the melamine polyphosphate family, melamine-poly(aluminium phosphate) (Safire®200), that has shown flame retardancy along with aluminium phosphinate in glass-fibre reinforced polyamide 66 was investigated to elucidate their mode of action. The mechanistic investigation is based on examining the chemical species formed in the condensed and gas phase under different fire scenarios. Samples at different stages of degradation were collected based on the heat release rate (HRR) curve of cone calorimetry and further analysed. Additionally, formulations and flame retardants were also pyrolysed at characteristic temperatures in a tubular furnace based on their thermogravimetric analysis (TGA) profile and investigated. A fire retardancy-quenching mechanism is mapped out on the basis of input from solid state nuclear magnetic resonance spectroscopy (MAS NMR; 27Al, 31P and 13C), Fourier transform Infra-red spectroscopy (FTIR), X-ray powder diffraction (XRD), electron probe microanalysis (EPMA), scanning electron microscopy (SEM), and optical microscopy on degraded samples. Gas phase analysis was studied by TGA coupled FTIR.

Protection mechanism of a flame-retarded polyamide 6 nanocomposite

Investigations have been performed to determine the causes of the synergistic effect observed when a combination of flame retardants (FR; aluminum phosphinate/melamine polyphosphate) and organomodified montmorillonite (o-MMT) is used in polyamide 6 (PA6). Structures obtained at different stage of degradation in cone calorimeter experiments for the PA6, PA6/FR, PA6/o-MMT, PA6/FR/o-MMT are compared. The evolution of the chemical species formed according to the stages of degradation together with the characterization of the resistance of the char have enabled to elucidate the mechanism of protection involved for PA6/FR/o-MMT. Infrared characterizations have demonstrated that the species formed are degradation products of the components of the formulation that are also observed for PA6/FR and PA6/o-MMT and do not explain the improved performances. However, the structure of the char with clay distinguishes itself with a very specific small closed-cells foamed structure exhibiting an enhanced char strength. A detailed comparison of the mode of protection involved when using FR and a combination of FR/o-MMT when submitted to fire is proposed.

Flame retardancy and mechanical properties of flax reinforced woven for composite applications

This paper investigates the flame retardant and mechanical properties of a flax woven fabric that can be used to prepare biocomposites. The flame retardant properties of the fabric are first considered using different ammonium phosphate salts and intumescent systems. It is demonstrated that satisfactory performances can be achieved using this approach. Better performances were obtained with pure phosphate salts in comparison to intumescent systems. This was attributed first, to the carbonization effect of the flax that could thus react with the phosphate and/or its degradation products leading to a stabilisation of the system and second to the lower phosphorus content when the full intumescent system is considered. On the other hand, despite a loss of biaxial tensile properties, the ability of the fire retardant treated fabric to form complex shape such as a tetrahedron was successfully demonstrated. Finally, the flame retardant properties of one-ply composites, using a bio-based matrix (Bioplast from Biotec), was evaluated. It was shown that good fire retardancy performances could be achieved considering only the flame retardancy of the reinforcement phase. This approach has potential for developing future flame retarded biocomposites.

Intumescence as method for providing fire resistance to structural composites: application to poly(ethylene terephtalate) foam sandwich–structured composite

Intumescence is a method for providing fire resistance to composite materials. In this paper, the fire resistance of intumescent coatings protecting structural composites (polyethylene terephthalate (PET) foam sandwich–structured composite) is evaluated at both the small and large scales according to the fire scenario described by the Steiner tunnel (ASTM E84). Results show acceptable correlations between the two scales and the approach developed at the small scale permits the fast screening of intumescent paints to predict their fire behavior at the large scale. It has been shown that intumescent paints protect efficiently the PET foam structured sandwich–structured composite used in the ceiling of railway station against fire.

Study of the Relationship Between Flammability and Melt Rheological Properties of Flame-Retarded Poly(Butylene Terephthalate) Containing Nanoclays

Recent studies on a new class of flame retardant (FR) systems that contain nanoclay and conventional FR microparticles have shown that the threshold concentration of FR required to achieve acceptable levels of flame retardancy can be significantly reduced in the presence of nanoclay. Bourbigot et al...

Modelling Behaviour of a Carbon Epoxy Composite Exposed to Fire: Part I—Characterisation of Thermophysical Properties

Thermophysical properties of a carbon-reinforced epoxy composite laminate (T700/M21 composite for aircraft structures) were evaluated using different innovative characterisation methods. Thermogravimetric Analysis (TGA), Simultaneous Thermal analysis (STA), Laser Flash analysis (LFA), and Fourier Transform Infrared (FTIR) analysis were used for measuring the thermal decomposition, the specific heat capacity, the anisotropic thermal conductivity of the composite, the heats of decomposition and the specific heat capacity of released gases. It permits to get input data to feed a three-dimensional (3D) model given the temperature profile and the mass loss obtained during well-defined fire scenarios (model presented in Part II of this paper). The measurements were optimised to get accurate data. The data also permit to create a public database on an aeronautical carbon fibre/epoxy composite for fire safety engineering.

Modelling Behaviour of a Carbon Epoxy Composite Exposed to Fire: Part II—Comparison with Experimental Results

Based on a phenomenological methodology, a three dimensional (3D) thermochemical model was developed to predict the temperature profile, the mass loss and the decomposition front of a carbon-reinforced epoxy composite laminate (T700/M21 composite) exposed to fire conditions. This 3D model takes into account the energy accumulation by the solid material, the anisotropic heat conduction, the thermal decomposition of the material, the gas mass flow into the composite, and the internal pressure. Thermophysical properties defined as temperature dependant properties were characterised using existing as well as innovative methodologies in order to use them as inputs into our physical model. The 3D thermochemical model accurately predicts the measured mass loss and observed decomposition front when the carbon fibre/epoxy composite is directly impacted by a propane flame. In short, the model shows its capability to predict the fire behaviour of a carbon fibre reinforced composite for fire safety engineering.

Intumescent Polymer Metal Laminates for Fire Protection

Intumescent paints are applied on materials to protect them against fire, but the development of novel chemistries has reached some limits. Recently, the concept of “Polymer Metal Laminates,” consisting of alternating thin aluminum foils and thin epoxy resin layers has been proven efficient against fire, due to the delamination between layers during burning. In this paper, both concepts were considered to design “Intumescent Polymer Metal Laminates” (IPML), i.e., successive thin layers of aluminum foils and intumescent coatings. Three different intumescent coatings were selected to prepare ten-plies IPML glued onto steel substrates. The IPMLs were characterized using optical microscopy, and their efficiency towards fire was evaluated using a burn-through test. Thermal profiles obtained were compared to those obtained for a monolayer of intumescent paint. For two of three coatings, the use of IPML revealed a clear improvement at the beginning of the test, with the slopes of the curves being dramatically decreased. Characterizations (expansion measurements, microscopic analyses, in situ temperature, and thermal measurements) were carried out on the different samples. It is suggested that the polymer metal laminates (PML) design, delays the carbonization of the residue. This work highlighted that design is as important as the chemistry of the formulation, to obtain an effective fire barrier.