Search

This study concerns the one-step radiografting of flax fabrics with phosphonated and fluorinated polymer chains using (meth)acrylic monomers: dimethyl(methacryloxy)methyl phosphonate (MAPC1), 2-(perfluorobutyl)ethyl methacrylate (M4), 1H,1H,2H,2H-perfluorooctyl acrylate (AC6) and 1H,1H,2H,2H-perfluorodecyl methacrylate (M8). The multifunctionalization of flax fabrics using a pre-irradiation procedure at 20 and 100 kGy allows simultaneously providing them with flame retardancy and hydro- and oleophobicity properties. The successful grafting of flax fibers is first confirmed by FTIR spectroscopy. The morphology of the treated fabrics, the regioselectivity of grafting and the distribution of the fluorine and phosphorus elements are assessed by scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The flame retardancy is evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. The hydro- and oleophobicity and water repellency of the treated fabrics is established by contact angle and sliding angle measurements, respectively. The grafting treatment of flax irradiated at 100 KGy, using M8 and MAPC1 monomers (50:50) for 24 h, allows achieving fluorine and phosphorus contents of 8.04 wt% and 0.77 wt%, respectively. The modified fabrics display excellent hydro-oleophobic and flame-retardant properties with water and diiodomethane contact angles of 151° and 131°, respectively, and a large decrease in peak of heat release rate (pHRR) compared to pristine flax (from 230 W/g to 53 W/g). Relevant results are also obtained for M4 and AC6 monomers in combination with MAPC1. For the flame retardancy feature, the presence of fluorinated groups does not disturb the effect of phosphorus.

Polymeric aluminum organophosphates are a class of nanostructured aluminum-based compounds that can be considered organic and inorganic hybrid materials. Aluminum phosphates have attracted considerable interest due to their ability to enhance composite materials’ mechanical characteristics, lightweight, and thermal properties. Extensive studies have shown the potential of aluminum organophosphates as a component in the development of fire-retardant materials. Aluminum–organophosphorus hybrid (APH) materials have been prepared by reacting aluminum oxide hydroxide (boehmite) with alkyl and aryl phosphoric acids and used to prepare composites with epoxy resin. Boehmite is an aluminum oxide hydroxide (γ-AlO(OH)) mineral, a component of the aluminum ore bauxite. In this work, the composites based on epoxy resin Epidian 601 and commercial curing agent IDA were obtained. Pure boehmite and APH hybrids were added as flame retardants. FTIR and TGA analysis showed that obtained APH possesses a hybrid structure, high thermostability, and various morphologies. These new APH were incorporated into epoxy resin. The infrared spectroscopy confirmed the structure of hybrids and composites. Pyrolysis combustion flow calorimetry (PCFC) and cone calorimeter analyses were performed to assess the flame retardant properties of the composites. The results showed that the incorporation of 17 wt% APH allows a reduction of heat release rate but to a limited extent in comparison to pure boehmite, which is due to the different decomposition mechanisms of both boehmite and hybrids. The cone calorimetry test showed that residue contents correspond quite well to the mineral fraction from boehmite only. The hybrid APHs appear no more efficient than pure boehmite because the mineral fraction in APH is reduced while phosphate fraction cannot promote significant charring.

In engineering applications, natural fiber composites must comply with fire requirements including the use of flame retardant. Furthermore, biocomposites are known to be water sensitive. Whether flame retardants affect the water sensitivity and whether water absorption affects the fire behavior and the mechanical performance of biocomposites are the two main topics addressed in this work. In this study, a flax fiber/epoxy composite flame retardant with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) or aluminum diethyl phosphinate (AlPi) was aged in humid atmosphere or by immersion in water. Water absorption kinetics revealed that DOPO induces an increase in equilibrium water content by approximately a factor of 2 due to its intrinsic hygroscopicity and/or its plasticizing effect on the epoxy matrix. In contrast, AlPi does not significantly change the water sensitivity of the biocomposite. Mechanical testing highlighted that, whatever the FR, the evolution of mechanical properties with ageing is governed by the moisture content. The drop of elastic modulus was attributed to a decrease in fiber rigidity due to plasticization, while the increase in tensile strength was assigned to an increase in fiber/matrix friction due to fiber swelling. As regards flame retardancy, only the highest water contents modified the fire behavior. For the AlPi containing biocomposite, the water release resulted in an increase by 50% of the time to ignition, while for the DOPO flame retardant biocomposite the water release was mainly postponed after ignition.

In French Guiana, the development of bio-circular value chains to convert residual biomass into insulation fiberboard represents a promising opportunity to build energy-efficient houses. The objectives of this work are to select and characterize resources of interest and discuss the relationships between fiber properties, manufacturing parameters and fiberboards performances. Five local wood and bark residuals fibers are fractionated and fractions are analyzed by laser granulometry, thermal gravimetric analysis (TGA) and pyrolysis combustion flow calorimeter (PCFC). Fiberboards are produced using a thermomechanical process and their microstructure, thermal and sorption properties are characterized by X-ray microtomography, hot plate technique, and dynamic vapor sorption (DVS). Morphological analysis shows that large and elongated wood fractions allow the formation of thick and cohesive fibrous networks, while the bark small-sized fractions are more difficult to process, requiring more compaction and synthetic fibers as additives. However, despite processing difficulties, bark fiberboards show the best insulation performances, comparable to commercial reference products. In addition, TGA and PCFC tests reveal that bark fibers show better thermal stability and fire behavior compared to wood. Finally, they also show a strong affinity for water, highlighting the need for further investigations on their ageing under tropical conditions of use.

International audience; By combining chemical and gamma radiation treatments, we show that it is possible to improve the interfacial adhesion between natural fibres and a non-polar and non-reactive matrix such as low density polyethylene (LDPE), and the resulting mechanical performances of their biocomposites. To this aim, flax fibres are first functionalized with octadecylphospho-nic acid (ODPA) and the quantity, effective grafting and localization of ODPA molecules on flax fibres are characterized by ICP-AES, solid state 31 P NMR and SEM-EDX. ODPA molecules are effectively grafted onto flax fibres at a content of roughly 2.5 wt% and mostly localized at the fibre surface. Moreover, contact angle measurements as well as water sorption kinetics give evidence for increased hydrophobic and oleophilic character of ODPA treated fibres. Pellets of LDPE/flax fibre biocomposites obtained by melt extrusion are then submitted to gamma radiation and processed by injection moulding. Based on Soxhlet extraction experiments and SEM observations, it is shown that LDPE cross-linking rate induced by gamma radiation is locally enhanced at the fibre/ma-trix interface, suggesting that regio-selective cross-linking occurred between LDPE chains and the alkyl chain of ODPA grafted on flax fibre surface. Consequently , the uniaxial tensile performances of the biocomposites are enhanced by this combined chemical and radiation-induced grafting approach, especially their ultimate properties (up to 40% increase in the work of rupture). These results evidence an enhanced interfacial adhesion that is also supported by more cohesive interfacial failure and higher work of rupture through in-situ micro-mechanical tensile SEM experiments.

International audience; Integrating bio-resources in materials allows to reduce the environmental impact of the building industry. This study deals with fire-retardant treatments, alternative to boric acid and ammonium salts solutions, applied to hemp fibers for thermal insulation application. The aim is to limit the energy, sanitary and environmental impacts of the treatment, while optimizing the technical performances. A laboratory protocol evaluates the flame-retardant effect of the developed treatments. Treated fibers, including commercial treatments, are subjected to characterization tests: direct ignition small flame, thermal analysis (thermogravimetric analysis [TGA], differential thermal analysis [DTA]), pyrolysis-combustion flow calorimeter and cone calorimeter. Some of the methods have been adapted to be applied to fibrous materials. The obtained results orientate the formulation of a treatment and highlight the complementarity of the analysis methods. Coupling the results, the ConeTools's predictive model leads to the estimation of the reaction to fire class according to the Euroclass. Euroclass C appears accessible with a tailored treatment.

An efficient, environmentally friendly flame-retardant process for lignocellulosic material was developed based on a renewable phosphorus flame retardant. The whole process which is easy to implement and to scale up is patented. The effectiveness of the treatment was proved by the analyses of pyrolysis-combustion flow calorimetry (PCFC), a flame test, X-ray fluorescence, 31P and 13C NMR and optical microscopy. Grafting of ≈ 0.5%P and ≈ 0.7% N was sufficient to produce a non-flammable material by a synergistic P/N effect. This process was successfully applied to cellulosic fibers and wood particles for the production of fire-resistant wood panels. The analysis of these panels showed not only an efficiency in fire behavior but also an improvement in mechanical and hygroscopic properties. The implementation of the process in different industrial production lines will be exposed.

The assessment of the modes of action of flame retardants (FRs) and their quantification is a challenging issue. This study highlights that the condensed phase efficiency θ can be assessed by combining different flammability tests (pyrolysis-combustion flow calorimeter PCFC, Limiting Oxygen Index LOI, cone calorimeter). Relations were proposed to calculate LOI and pHRR in cone calorimeter from several parameters including θ. A satisfying agreement between experimental values and calculated ones were found for a set of several dozens of FR-free polymers assuming that θ = 1 (i.e. no action in condensed phase).Then, θ was evaluated for EVA/PE blends containing Aluminium TriHydroxyde (ATH) and/or Magnesium DiHydroxyde (MDH) and for ABS containing Ammonium PolyPhosphate (APP) and/or DecaBromoDiPhenylOxide (DBDPO) assuming that LOI and pHRR of flame-retardant compositions follow the same relationships as those of unfilled polymers. The evolution of θ (as well as χ, i.e. the combustion efficiency) highlights the modes of action of FRs and can contribute to the discussion about possible synergy or antagonism between FRs. Especially, an apparent synergism between APP/DBDPO is observed in cone calorimeter from a performance point of view. Nevertheless, the calculation of χ and θ challenges this conclusion.

Alkyd resins occupy a prominent place among the coating industry [1]. However, they have two major drawbacks, the presence of solvents as volatile organic compounds and their high flammability[2,3,4]. The present work investigates a two-in-one solution by setting up novel phosphonate and phosphate cardanol-based reactive diluents with flame retardant properties for alkyd resins. The alkyd resins were applied as coatings on wood surface and their fire behaviors were investigated. All the results have exhibited an improvement of FR properties with the increase of phosphorus content, demonstrating an action in condensed phase by promoting char formation for phosphonate and phosphate compounds. The most promising results were obtained with 2 wt% of phosphate in the alkyd resin formulation and exhibited a 41 % reduction in pHRR compared to the resins without phosphorus-containing cardanol diluent.

Également publié le 15/10/2021 sous la référence FR3109113; The present invention relates to a flame retardant treatment of a lignocellulosic material, characterized in that it comprises the following steps: - optionally steam explosion of the lignocellulosic material, - impregnation of the optionally steam-exploded lignocellulosic material, in or with an aqueous solution comprising from 0.5% to 10% of phytic acid and from 1% to 30% of urea, and preferably from 3% to 7% of phytic acid and from 15% to 22% of urea, said percentages being expressed by weight relative to the total weight of the aqueous solution, - optionally drying of the impregnated lignocellulosic material, until it has a moisture content ranging from 5% to 20%, said percentages being expressed by weight relative to the total weight of the impregnated lignocellulosic material, - cooking of the impregnated and optionally dried lignocellulosic material, the resulting flame-retarded lignocellulosic material comprising a content of phosphorus originating from the phytic acid ranging from 0.1% to 10%, preferably ranging from 0.3% to 3%, said percentages being expressed by weight relative to the total weight of the flame-retarded lignocellulosic material. The invention also relates to the resulting flame-retarded lignocellulosic material and the use thereof for manufacturing: - flame-retarded composite materials based on plant fibres, - woven or nonwoven flame-retarded flexible materials based on plant fibres, and particularly textiles, - flame-retarded materials based on wood fibres and/or on wood particles, and particularly flame-retarded wood panels.; La présente invention a pour objet un procédé d’ignifugation d’une matière lignocellulosique caractérisé en ce qu’il comprend les étapes suivantes :- éventuellement explosion à la vapeur de la matière lignocellulosique,- imprégnation de la matière lignocellulosique, éventuellement explosée à la vapeur, dans ou avec une solution aqueuse comprenant de 0,5% à 10% d’acide phytique et de 1% à 30% d’urée, et de préférence de 3% à 7% d’acide phytique et de 15% à 22% d’urée, lesdits pourcentages étant exprimés en masse par rapport à la masse totale de la solution aqueuse,- séchage de la matière lignocellulosique imprégnée, jusqu’à ce qu’elle présente une humidité allant de 5% à 20%, lesdits pourcentages étant exprimés en masse par rapport à la masse totale de la matière lignocellulosique imprégnée,- cuisson de la matière lignocellulosique imprégnée et séchée,la matière lignocellulosique ignifugée ainsi obtenue comprenant une teneur en phosphore provenant de l’acide phytique allant de 0,1% à 10%, de préférence allant de 0,3 % à 3%, lesdits pourcentages étant exprimés en masse par rapport à la masse totale de la matière lignocellulosique ignifugée. L’invention concerne encore la matière lignocellulosique ignifugée ainsi obtenue et son utilisation pour la fabrication :- de matériaux composites ignifugés à base de fibres végétales,- de matériaux souples ignifugés tissés ou non tissés à base de fibres végétales, et notamment de textiles,- de matériaux ignifugés à base de fibres de bois et/ou de particules de bois, et notamment de panneaux de bois ignifugés.

In order to get new insights on cable behavior during real-scale fires, the gases released under incomplete combustion in pyrolysis combustion flow calorimeter were recorded for several PVC and halogen-free flame-retardant cables. Incomplete combustion was monitored by changing combustion temperature between 600 and 900 °C. Gases were identified using PCFC–FTIR coupling. Quantitative assessment of different gases produced during combustion was also carried out. It appears that larger amounts of unburnt gases are produced for PVC cable at low temperature (

International audience; Designing innovative multi-functional thermoset polymers represents a major challenge in materials science. In this work, two novel polyhedral imidazolium ionic liquid supported on oligomeric silsesquioxane nanocages having chloride (Cl-) and bistrifluoromethanesulfonimidate (NTf2-) counter anions have been synthesized. These ionic nano-objects were used to nanostructure a model epoxy network. Hence, networks displaying a homogeneous nanoscale morphology were obtained by introducing 5wt % of such organic-inorganic (O/I) silicon-oxo clusters functionalized with ionic liquids. The obtained ionic hybrid O/I epoxy-amine networks display an excellent thermal stability (> 400 °C) compared to their neat counterparts, as well as a pronounced hydrophobic character (23 mJ m-2) and good mechanical performances. Moreover, these O/I nanostructured networks demonstrate an improved fire resistance according to pyrolysis-combustion flow calorimetry (PCFC) and cone calorimetry analyses. In fact, the use of low amounts of imidazolium ionic liquid-modified polyhedral oligomeric silsesquioxanes induce a significant decrease of heat release rate (about 55 %), as well as a retardation of the ignition time (close to 29 %) compared to the neat epoxy-amine network.

International audience; The ignition of four different PVC-based electric cables was studied using cone calorimeter and the influence of the charring phenomenon on ignition was investigated. The thermophysical and optical properties of the sheaths before decomposition were measured. The kinetics of charring was studied by photogrammetry. It was shown that charring occurs for three cables before ignition at heat flux lower than 45 kW/m2. The lower is the heat flux, the higher is the char amount at ignition. In spite of the char formation, it was observed that the time-to-ignition of the cables can be properly calculated using the well-known Quintiere’s equation, considering an apparent temperature of ignition. This apparent temperature at ignition was found in the range 312°C to 349°C for the four electric cables.

International audience; Wood-plastic composites were prepared by impregnating softwood and tropical hardwood by a radiation-curing resin containing phosphorus or chlorine groups as flame retardant. Microscopic observations revealed that the heterogeneous impregnation depends on the density but also on the wood species and sample orientation. Physical properties (hardness, stiffness, conductivity, water content) of the unmodified woods and their resin-impregnated counterparts were examined and correlated with their densities. The flame retardancy was investigated by cone calorimeter tests. Although the incorporation of the resin is detrimental to the flame retardancy, the addition of phosphorus or chlorine groups allows a decrease in flammability. Phosphorus-containing resins limit the smoke release in comparison to chlorine-containing resin. Finally, the denser wood-plastic composites exhibit improved mechanical properties without increasing the flammability in comparison with their unmodified wood counterparts.

International audience; Various phosphorus flame retardants (FR) have been grafted on lignin-rich miscanthus fibers and lignin-poor flax fibers according to two methods, phosphonic acids condensation in mild conditions and radiation grafting. Phosphorus content and its location on fibers were evaluated. Even if phosphorus FR diffused into the fibers bulk in all cases, chemical modification based on phosphonic acids condensation with hydroxyls of miscanthus fibers appears more suitable for high lignin content fibers. Phosphorus content in miscanthus fibers reached 1.4 wt% using hexane-1,6-diylbisphosphonic acid whereas it reached a lower content (0.3 wt%) for flax fibers. Radiation grafting is suitable for both fibers with limited effect depending on fiber nature. Flame retardancy at microscale was examined using PCFC and TGA. Thermal properties and flame retardancy have been shown to be correlated to the phosphorus content but also to fibers composition and to the thermal stability of the flame retardant. Vinyl phosphonic acid was found to be more efficient as char promoter for flax compared to miscanthus.

International audience; A new biosourced composite foam (AF, associating foamed alginate matrix and orange peel filler) is successfully tested for fire-retardant properties. This material having similar thermal insulating properties and density than fire-retardant polyurethane foam (FR-PUF, a commercial product) shows promising enhanced properties for flame retardancy, as assessed by different methods such as thermogravimetric analysis (TGA), pyrolysis combustion flow calorimetry (PCFC) and a newly designed apparatus called RAPACES for investigating large-scale samples. All these methods confirm the promising properties of this alternative material in terms of fire protection (pHRR, THR, EHC, time-to-ignition, flame duration or production of residue), especially for heat flux not exceeding 50 kW m−2. At higher heat flux (i.e., 75 kW m−2), flame retardant properties tend to decrease but maintain at a higher level than FR-PUF. The investigation of the effect of AF thickness shows that the critical thickness (CT) is close to 1.5–1.7 cm: heat diffusion and material combustion are limited to the CT layer that protects the underlying layers from combustion. A multiplicity of factors can explain this behavior, such as: (a) negligible heat conduction, (b) low heat of combustion, (c) charring formation, and (d) water release. Water being released from underlying layers, dilutes the gases emitted during the combustion of superficial layers and promotes the flame extinction.

International audience; The interactions between kaolinite and a commercially available phosphinate-based flame retardant (Exolit® OP1311) were evaluated as flame retardant systems in Polyamide 6 (PA6). The thermal degradation and flammability of PA6 composites were studied by TGA and cone calorimeter tests. Characterizations were conducted using FTIR, EDX and XRD. Cone calorimeter results showed a reduction in peak heat release rate (pHRR) as a function of filler loading and type with a greater reduction for OP1311 containing composites. Interestingly, OP1311 can be partially substituted by kaolinite without detrimental effect on peak of release rate (pHRR) measured by cone calorimeter. FTIR, EDX and XRD analysis of cone calorimeter residues showed that kaolinite may trap some phosphorous compounds in condensed phase leading to the formation of a glassy structure on sample residue. To assess possible interactions between kaolinite and phosphinate, a controlled thermal degradation was carried out on kaolinite, OP1311 and kaolinite/OP1311 (50:50) blends. The residues were analyzed by EDX and XRD. Results showed that almost all phosphorous present in the initial sample remains in residue for Kaolinite/OP1311 blend versus only about 60% for OP1311 alone. Also, XRD results showed that during combustion, new crystalline phases can be formed in the sample when kaolinite is combined with OP1311. These results suggest that some interactions between both components may occur and could explain the observed fire behavior of the composites containing kaolinite and phosphinate.

International audience; Achieving a complete curing of biocomposites without damaging fibers is very challenging. This study assesses the impact of processing upon the mechanical properties of a unidirectional flax reinforced epoxy composite and identifies which component (resin, reinforcement or interphase) is the most sensitive to post-curing at high temperature (100, 120 or 150°C). Post-curing temperature had a limited impact on the composite mechanical behavior excepted at 150°C where ultimate stress and strain decreased drastically while the stabilized modulus slightly increases.Post curing is responsible of a slight decrease of the matrix tensile properties attributed to the polymer oxidation but cannot explain on its own the evolution of the composite behavior. Interfacial adhesion played a minor role in the composite behavior probably due to its intrinsic weakness. Finally, the flax fabric was highlighted to be the component most sensitive to thermal treatment thus governing the drop in the composite mechanical properties.

International audience; 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.

International audience; This work seeks to address the effect of simultaneous use of three flame retardants, having three different modes of action, (magnesium hydroxide, expanded and expandable graphite) on the thermal degradation and flame retardancy of poly(ethylene-co-vinyl acetate). Thermal conductivity of samples was measured in order to investigate the effect of the use of expanded and expandable graphite on the time-to-ignition and the peak of heat release rate in cone calorimeter test. Thermal shielding performances of chars were studied as well. It was found that there is an optimum ratio between expanded and expandable graphite in order to control thermal conductivity and therefore fire properties. Some correlations were also found between the char thickness and the first peak of heat release rate.

International audience; 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.

From a set of around 100 phosphorus-containing polymers tested in pyrolysis&ndash, combustion flow calorimetry, the contributions to flammability of two phosphorus-containing pendant groups (called 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and PO3) were calculated using an advanced method previously proposed and validated. The flammability properties include total heat release (THR) and heat release capacity (HRC) measured in standard conditions, i.e., anaerobic pyrolysis and complete combustion. The calculated contributions are in good agreement with the main modes of action of both phosphorus groups, i.e., flame inhibition for DOPO and char promotion for PO3. Moreover, the results provide first conclusions about the cooperative interaction between phosphorus and nitrogen, as well as the influence of the architecture of tested co-polymers.

A biobased reactive phosphate flame retardant derived from isoeugenol was synthesized and fully characterized (1H, 13C, 31P NMR, FTIR, MS) with the aim of improving flame retardancy behavior of bio...

International audience; Wood is a widely used material in the construction sector, both in structural and non-structural applications. Tropical species are appreciated for their high quality and durability in furniture, outdoor and indoor claddings and floors. However, limited information exists about fire reaction of tropical wood. Density is one of the factors that influence the rate of pyrolysis reactions and consequently the charring rate. However, other wood characteristics such as the mineral content also exert an influence on the pyrolysis combustion of wood. Hardwoods present a complex morphological structure and a significant amount of minerals, extracts and exudates. In this work, we study the fire reaction of seven species of tropical hardwood using various fire tests. Results are compared from one test to other one and are discussed in relation with physicochemical properties of wood species. The results show that although there is some correlation between high density and ignition time, parameters such as morphology and mineral content are also relevant.