Search

Co-product of sunflower cultivation, pith of stem has a little exploited insulating potential. Blocks in which pith particles are glued together using a starch-based binder have already been obtained. However, they are highly water-sensitive. Replacing this binder with others has been considered here. Polysaccharide-based binders were tested, chosen for their more hydrophobic character: sodium alginate, chitosan, Citrus pectin, and a modified starch. Like starch, these binders are physically binding. They are first solubilised in water (except chitosan, dissolved in 2% acetic acid). The solution is then mixed with pith particles before cold compression molding for 90 s. A 10% binder content was initially considered. The blocks were all cohesive with a dry density from 36 to 42 kg/m3). Their performances were assessed through water absorption capacity and resistance via capillary absorption tests on wet sponges, mechanical test and thermal conductivity. Chitosan and pectin-based blocks show the best properties, particularly concerning water resistance and mechanical properties. The pectin-based block has improved its elastic modulus by 40% compared to a starch-based block. The pectin-based block in its case absorbs 2.7 times less water than starch. Finally, thermal conductivities of pectin and chitosan-based pith blocks are in the same order of magnitude as for starch (39.8-40.1 mW/m.K), and close to values from commercial materials (e.g., polystyrene). Pectin and chitosan were also tested at three rates (5%, 10% and 15%). A significant improvement in the blocks' compressive strength was observed with the increase in binder rate, while thermal conductivities varied little.

International audience; Linseed flax is a multipurpose crop. It is cultivated for its seeds and particularly for its oil. The main contributors for this crop are Canada, France and Belgium. In general, straws of linseed flax are buried in the fields or burnt. However, these solutions are not good practices for the environment and from an economical point of view. In this study, straws of linseed flax (six batches in total) with different dew retting durations and harvesting techniques were studied to possibly use them for producing innovative geotextiles. Two different fibre extraction processes were investigated. A first process (A) involved horizontal breaker rollers and then a breaking card. A second one (B) consisted in using vertical breaker rollers, and an “all fibre” extraction device (fibre opener) followed by sieving. The chemical composition of fibres in parietal constituents appeared to be globally equivalent to the one of textile flax with a pectic content decreasing as a function of the dew retting duration. This contributed to an increase in the cellulose content. The fibre content was situated in a range from 29% to 33%, which corresponds to a good yield for linseed flax fibre. The level of purity can reach values of up to 90% for method A (without extra-sieving) and 96% for method B (with extra-sieving), and the length of the fibres (larger for method A than for method B) and their tensile properties make them suitable for structural geotextile yarn manufacturing.

International audience; A versatile twin-screw extrusion process to provide an efficient thermo-mechano-chemical pre-treatment on lignocellulosic biomass before using it as source of mechanical reinforcement in fully bio-based fiberboards was developed. Various lignocellulosic crop by-products have already been successfully pre-treated through this process, e.g., cereal straws (especially rice), coriander straw, shives from oleaginous flax straw, and bark of both amaranth and sunflower stems.The extrusion process results in a marked increase in the average fiber aspect ratio, leading to improved mechanical properties of fiberboards. The twin-screw extruder can also be fitted with a filtration module at the end of the barrel. The continuous extraction of various chemicals (e.g., free sugars, hemicelluloses, volatiles from essential oil fractions, etc.) from the lignocellulosic substrate, and the fiber refining can, therefore, be performed simultaneously.The extruder can also be used for its mixing ability: a natural binder (e.g., Organosolv lignins, protein-based oilcakes, starch, etc.) can be added to the refined fibers at the end of the screw profile. The obtained premix is ready to be molded through hot pressing, with the natural binder contributing to fiberboard cohesion. Such a combined process in a single extruder pass improves the production time, production cost, and may lead to reduction in plant production size. Because all the operations are performed in a single step, fiber morphology is better preserved, thanks to a reduced residence time of the material inside the extruder, resulting in enhanced material performances. Such one-step extrusion operation may be at the origin of a valuable industrial process intensification.Compared to commercial wood-based materials, these fully bio-based fiberboards do not emit any formaldehyde, and they could find various applications, e.g., intermediate containers, furniture, domestic flooring, shelving, general construction, etc.

Controlled-release fertilizers (CRF) are needed under current agriculture practice to decrease the environmental impact caused by fertilizer doses applied in excess of plants&rsquo, uptake rate. Commercial CRF are available. They are manufactured from mineral fertilizers encapsulated into a synthetic polymer matrix or coated by a polymer layer. However, substitution of fossil sourced organic polymers with biopolymers is a major environmental concern. In the present paper, we describe the manufacture by a continuous twin-screw extrusion process, and the mechanical and chemical properties of injection-molded composite pellets containing 90% sunflower protein concentrate (SPC) matrix, and 5&ndash, 10% of a biopolymer (BP) obtained from municipal biowastes (MBW), and/or urea (U). The reported results show that SPC-BP-U behaves as an efficient eco-friendly CRF. BP contributes to several benefits to the performance of the composite pellets, upon increasing surface hardness, and controlling the formation of ammonia from urea hydrolysis and the release of organic nitrogen. The SPC-BP-U appears a powerful eco-friendly CRF to supply organic C and the three major N, P, and K nutrients to soil and plants. It offers worthwhile scope for being tested in the cultivation of specific plants under the real operational conditions of agriculture practices.

International audience; This work describes a process approach to study the oil leakage phenomenon in feeds for large Trout. Using a pilot vacuum coater, four experimental coating parameters were studied (stirring speed, pressure, filling rate, and time needed to restore atmospheric pressure) through an experimental design. The properties measured on the coated pellets were the oil leakage rate and three other important usage properties, i.e. durability, hardness, and floatability. The coating conditions had a significant influence on oil leakage rate, varying at 40 °C from 2.7 % to 1.2 % depending on the coating conditions used. Finally, the vacuum level was the most effective factor in reducing leakage. Indeed, a progressive reduction in oil leakage rate was observed as the pressure inside the coater was reduced during coating.

International audience; Nowadays, amaranth appears as a promising source of squalene of vegetable origin for the cosmetic industry. Squalene represents up to 6% (w/w) of oil from seeds. It can be isolated from vegetable oil forsubsequent use. This triterpene is highly appreciated in cosmetology, especially for the formulation of moisturing creams. Indeed, it has the ability to quickly penetrate the skin without leaving traces or oilysensations on it, and it blends well with other oils and vitamins. The squalene currently marketed is almost exclusively extracted from the liver of sharks, causing at the same time their overfishing. Thus, providing to the cosmetic industry a squalene of renewable origin is a major challenge for the cosmetic industry. As amaranth oil is one of the most concentrated vegetable oils in squalene, this is the reason why the amaranth plant has experienced renewed interest in recent years. In addition to the seeds, a stem is also produced during the amaranth cultivation. Representing up to 80% (w/w) of the plant aerial part, it is composed of a ligneous fraction, the bark, on its periphery, and a pith in its middle. In this study, a mechanical fractionation process was developed to separate continuously bark and pith. The use of both fractions to produce renewable materials for building applications was also investigated. On the one hand, the bark was succesfully used to produce hardboards, with the deoiled seeds acting as natural binder. Such boards are a viable alternative to commercial wood-based panels (e.g., plywood, chipboard, OSB or MDF). On the other hand, the pith was transformed with success into cohesive and machinable lowdensity insulation blocks revealing a thermal conductivity near from that of polystyrene.

International audience; Straw represents 60-80% of the aerial part of the coriander plant. Because of the increasing demand for vegetable oil from fruits for food, cosmetics or the chemical industry, the availability of straw will grow strongly in the future. Its high lignocellulose content (62%) makes this crop by-product an interesting raw material for producing bio-based building materials. Bulk materials can be obtained by refining the straw through twin-screw extrusion in the presence of water. The fiber aspect ratio of refined straw can be varied (22.9-26.5) by applying different liquid/solid ratios (0.4-1.0), leading to a variation in the tapped density of the resulting bulk material (110-61 kg/m3). For the lowest density, thermal conductivity is 47.3 mW/(m.K). Twin-screw refining can also be conducted from an aqueous borax solution. Refined straw thus becomes fire-proofed, making it usable as loose fill in housing. Insulation blocks of medium density, associating straw and a starch-based binder, can also be produced through compression molding. With a density of 155 kg/m3 and a thermal conductivity of 55.6 mW/(m.K), the optimal cohesive blocks (7.5 mm milled straw and 15% binder), cold-pressed at 87 kPa for 30 s, are promising alternatives for the thermal insulation of buildings (e.g., filling of walls, interior partitions, etc.).

Flax (Linum usitatissimum L.) has been grown since the antiquity for tis ability to provide fibres for the confection of clothes. It has also been used for the production of technical fabrics such as sails for example. In the 20th century, and particularly in Europe, the vegetal fibres such as flax were progressively replaced by synthetic fibres from petroleum origin. However, a large regain of interest for vegetal fibres and particularly for flax fibres was observed in the last 2 decades for using these fibres in challenging new applications for which the environmental impact is considered. Different varieties of Linum usitatissimum L. have been selected by breeder to optimise the production of fine long fibres (textile flax) or to optimise the production of seeds (linseed or oleaginous flax). In both cases, bast fibres can be extracted from the flax stems. This chapter shows that the fibres extracted from either textile or linseed flax varieties can be used for different technical textiles for high added value applications. In a first part, the chapter deals with the different processes used to extract and prepare the fibres for textile applications according to the growth and harvesting techniques considered. In a second part, different manufacturing processes or techniques to produce flax fibre non-woven and woven textiles for composite reinforcements are presented. A discussion about the interest of selecting a particular type of yarn or a particular 2D or 3D architecturation technique is also presented in relation to different composite requirements and applications. The third part of this chapter is dedicated to the interest of using flax fibres for non-woven and woven geotextile applications. Specificities associated to the use of biodegradable vegetal fibres are presented and solutions to control the degradation time of the textiles with a minimum impact on the environment are also discussed in the document.

International audience; This work assesses the potential of nettle (Urtica dioica L.) fibers produced on contaminated lands for composite applications. The nettles studied in this work grew spontaneously and in a prevalent manner in poplar short rotation coppice planted for the phytomanagement of a land contaminated by traces of metals. Results show that the contaminant contents in nettle bast fibers are low: only traces were measured. It makes it possible to consider this biomass for material use. The measured matter yield is lower than those obtained with traditional fiber crops cultivated in Europe on agricultural lands but the tensile properties of the bast fibers are equal to or better than those of hemp and flax, making spontaneous nettle an interesting supplement to traditional European fiber crops for composite applications

National audience; In this study, fiberboards were produced from shives collected after continuous fiber mechanical extraction from oleaginous flax straw. Fiberboards were produced through thermo-pressing, and their mechanical and thermo-mechanical properties were studied, as well as their water resistance. The influence of one pretreatment for shives and lignin addition was investigated on the different properties. Boards obtained were all cohesive hardboards. The optimal board was obtained from fibers extruded from shives and without addition of any supplementary lignin amount. Looking at its characteristics and standard NF EN 312, the latter perfectly complied with the requirements for type P1 boards, i.e. boards for general uses in dry conditions.; Dans cette étude, des panneaux agglomérés de fibres ont été produits à partir d’anas collectés après extraction mécanique des fibres libériennes de paille de lin oléagineux. Les panneaux ont été mis en oeuvre par thermopressage. Leurs propriétés mécaniques et thermo-mécaniques ont été étudiées ainsi que leur comportement vis-à-vis de l’eau. L’influence d’un prétraitement thermo-mécanique des anas bruts à l’aide d’une extrudeuse bi-vis a été étudiée ainsi que l’ajout de lignine exogène. Tous les panneaux mis en oeuvre possèdent une tenue suffisante pour être manipulés à la main. Le panneau ayant obtenu les propriétés optimales a été obtenu à partir des anas extrudés et sans ajout supplémentaire de lignine. Au regard de ses caractéristiques et du standard NF EN 312, ce dernier remplit complètement les critères d’un panneau aggloméré de type P1 (panneau d’usage général utilisé en milieu sec).

International audience; The objective of this study was to investigate the influence of fiber morphology and molding parameters on the mechanical and physical properties of fiberboards made from rice straw. The rice straw was thermomechanically treated with a twin-screw extruder. Three parameters were investigated: the amount of water added at molding (0–20%), lignin content (0–25%), and the liquid/solid ratio used for extrudate production (0.33–1.07). A Doehlert experimental design was used to evaluate the effects of these factors on fiberboard properties. A liquid/solid ratio of 0.4 at extrudate production, the addition of 5% water at molding, and a lignin content of 8.9% were found to be optimal for bending properties. The fiberboard produced in these conditions had a density of 1414 kg/m3 (i.e. the densest board). Maximum flexural strength and elastic modulus were 50.3 MPa and 8.6 GPa, respectively. A thickness swelling of 23.6% and 17.6% water absorption were observed. The statistical analysis suggested that a good compromise between density and flexural properties could be obtained with the addition of 0% water, a lignin content of 25% and a liquid/solid ratio of 0.33 at extrudate production. Polynomial models suggested that the fiberboards produced in such conditions would have a maximum flexural strength of 50 MPa, an elastic modulus of 6.0 GPa, a density of 1102 kg/m3, and a thickness swelling of 24%.

International audience; The development of materials based on renewable and low-cost resources is today’s crucial interest for civil engineering. This work intends to investigate two new vegetable fibers as composite reinforcement for insulation application in the building industry. Miscanthus and sunflower stalk have mainly been selected for their high fiber content, low water content after harvesting, and availability. These criteria lead to good structural properties and allow a reduction in production and transportation costs. This study aims at demonstrating the feasibility to produce cohesive panels from these lignocellulosic fibers and their related interesting mechanical and thermal properties according to various natural binders.

International audience; This work assesses the potential of stinging nettle (Urtica dioica L.) growing on trace element contaminated soils to produce fibres for material applications. The nettles studied in this work grew spontaneously and dominated the vegetation cover in poplar short rotation coppices planted for the phytomanagement of lands contaminated by trace elements. Two sites were studied, contaminated by Hg for the first one and a mix of As, Cd, Pb and Zn for the second one. Results show that, for the considered soils, the contaminant contents in nettle bast fibres were at low levels, comparable to those collected at unpolluted control areas. It makes it possible to consider this biomass for material use. The measured matter yield was lower than those obtained with traditional fibre crops cultivated in Europe on agricultural lands. However, the tensile properties of the bast fibres mechanically extracted without field retting or prior alkaline treatment were equal to or better than those of industrial hemp and flax, making spontaneous nettles an interesting supplement to traditional European fibre crops for material applications.

International audience; In this study, coriander straw fiber was effectively incorporated as a reinforcing filler in polypropylene and biobased low-density polyethylene composite materials through twin-screw extrusion compounding and injection molding. Maleic anhydride-grafted copolymers were added as a coupling agent and effectively provided fiber/matrix compatibilization. With a significant reinforcing effect, resulting in a 50% increase in the flexural and tensile strength (from 19 to 28 MPa and from 12 to 17 MPa, respectively, for polypropylene composites) as compared to the native polymer, coriander straw allowed the production of 40% filled thermoplastic biocomposites with adequate mechanical properties comparable to those of commercial wood fibers, excellent durability in terms of UV and hygrothermal weathering and high potential for recycling. At the same time, such coriander biocomposites show a favorable cost structure, with 28% reduction of the granule cost as compared to wood fiber composites.

The aim of this study consisted of manufacturing renewable binderless fiberboards from coriander straw and a deoiled coriander press cake, thus at the same time ensuring the valorization of crop residues and process by-products. The press cake acted as a natural binder inside the boards owing to the thermoplastic behavior of its protein fraction during thermopressing. The influence of different fiber-refining methods was evaluated and it was shown that a twin-screw extrusion treatment effectively improved fiber morphology and resulted in fiberboards with enhanced performance as compared to a conventional grinding process. The best fiberboard was produced with extrusion-refined straw using a 0.4 liquid/solid (L/S) ratio and with 40% press cake addition. The water sensitivity of the boards was effectively reduced by 63% through the addition of an extrusion raw material premixing operation and thermal treatment of the panels at 200 °C, resulting in materials with good performance showing a flexural strength of 29 MPa and a thickness swelling of 24%. Produced without the use of any chemical adhesives, these fiberboards could thus present viable, sustainable alternatives for current commercial wood-based materials such as oriented strand board, particleboard and medium-density fiberboard, with high cost-effectiveness.

International audience; Cultivated primarily for its seeds, oleaginous flax could also be valued for the different fractions that can be extracted from the straw. However, as the straws are not harvested with the same technique and care than for the textile flax, the classical scutching technique cannot be used. As a consequence, an “all fibre” device was used to perform the separation of the different constituents of the oleaginous flax straws. The different fractions were quantified for two retting levels and for two degrees of rewetting of the stems. The physical and mechanical properties of fibres were then evaluated. It appears that the relative amount of fibres extracted from oleaginous flax straw is comparable to the one from textile flax (i.e. 40% of the stem dry mass), and their tensile properties are situated in the lower part of the textile flax range. This work shows that the individual fibre length of oleaginous flax (between 3 and 6 cm) is comparable to that of the scutched textile flax fibres. This makes them suitable for the production of carded aligned fibre yarns for technical reinforcement textiles (e.g. composites or geotextiles). These results demonstrate the interest and the potential added value of harvesting the stems for technical fibre applications.

A deoiled press cake resulting from twin-screw extrusion of coriander fruits was used as a raw material for the production of self-bonded boards. The operating parameters for thermopressing were varied and include the applied pressure (19.6–39.2 MPa), molding time (60–300 s), and molding temperature (155–205 °C). The optimized process conditions (21.6 MPa, 300 s, 205 °C) resulted in a board with a density of 1323 kg/m3, a flexural strength of 23 MPa, a modulus of elasticity of 4.4 GPa, and a thickness swelling of 31%. The thickness swelling was effectively reduced to 20% through the application of a heat treatment at 200 °C after thermopressing. A variation of the moisture content of the press cake between 3 and 8% showed that increased moisture contents do not lead to improved mechanical properties of the resulting board and further induce internal fracturing of the board during thermopressing. The manufactured binderless boards may act as environmentally friendly alternatives to commercial wood-based boards such as oriented strand board and particleboard.

Poly(vinyl alcohol- co -ethylene) was compounded with 2–10% post-harvest tomato (PHT) plant powder and processed by single-screw extrusion to yield composite films. Upon increasing the filler content, the values of the mechanical properties indicators were found to decrease as follows: Young's modulus from 1797 to 750 MPa, stress at yield from 36 to 15 MPa, maximal stress from 39 to 15 MPa, stress at break from 35 to 14 MPa, and strain at break from 6.6 to 4.3%. The results are discussed in comparison with other composite films containing poly(vinyl alcohol- co -ethylene) and water soluble biopolymers obtained by alkaline hydrolysis of fermented municipal biowastes, and with other commercial materials, such as starch based and low density polyethylene mulch films. Depending on the intended application, the post-harvest tomato blend films may be competitive for cost, performance and sustainability.

International audience; Post-harvest tomato plants were used to manufacture fireboards by thermopressing. Four plant materials were investigated: exhausted tomato plants ground to 5-10 mm (PHTr), tomato (PHT) and maize (PHM) plants ground to

International audience; Single-screw extrusion allows obtaining composite films containing poly(ethylene-co-vinyl alcohol), hereinafter EVOH, and water-soluble lignin-like biopolymers (SLP) isolated from the alkaline hydrolysate of two materials sampled from an urban waste treatment plant. During extrusion, a condensation reaction occurs between the EVOH and SLP. The products are heterogeneous. They contain a mix of EVOH-SLP copolymers with different composition and solubility properties. The films were characterized for tensile strength and water sorption properties. Young modulus and strain at break, respectively, were 2.8 GPa and 14% for neat EVOH vs. 2.1-0.9 GPa and 17–4% for the blends containing 2–15% SLP, with values decreasing upon increasing the % SLP. The blends were more hydrophilic than neat EVOH; their water sorption capacity was found to increase upon increasing the SLP content. Compared to previously reported similar blends obtained by twin-screw extrusion and solvent casting, the data for the single-screw extruded films allows discussing several aspects connected to the valorisation of blends obtained from fossil and biowaste sourced polymers.

Biorefinery of sunflower whole plant was performed successfully using a thermo-mechano-chemical twin-screw reactor. This led to the aqueous extraction of oil and other biopolymers like proteins, pectins and non pectic sugars. It resulted in the overall fractionation of biomass, thus allowing a complete valorization of the input. This biorefinery process was not only efficient but it was also environment-friendly. In addition, it contributed to the production of different end products for various industrial applications. Firstly, the hydrophilic phase will be recycled to the process. Secondly, the densest oil-in-water emulsion is a promising candidate for the formulation of cosmetic creams. Thirdly, the upper hydrophobic phase will be usable for the waterproofing treatment of the surface of agromaterials by coating. Its demixing will also lead to the production of proteins with tensioactive properties. These will serve for the food industry. Lastly, the cake was a mixture of plasticized proteins and lignocellulosic fibers. It was thus considered as a natural composite. Its molding into cohesive fiberboards was conducted successfully using both thermopressing and compression molding processes. The self-bonded boards with high density will be suitable for use as load bearing boards in dry conditions (floor underlayers, interior partitions, furniture, etc.). Positioned in walls and ceilings, boards with medium and low density will contribute to the heat insulation of buildings. In addition, the bulk cake will be also usable as a loose fill insulation material. As proposed, this flow chart thus allows a valorization for all fractions originating from the twin-screw reactor., Le bioraffinage du tournesol plante entière a été réalisé avec succès en utilisant un réacteur thermo-mécano-chimique bi-vis. Cela a permis l’extraction aqueuse de l’huile et d’autres biopolymères tels que des protéines, des pectines et des sucres non pectiques. Un fractionnement total de la biomasse a été obtenu, permettant ainsi une valorisation complète de la matière entrante. À la fois efficace et respectueuse de l’environnement, cette bioraffinerie a généré plusieurs produits finaux pour diverses applications industrielles. Tout d’abord, la phase hydrophile pourra être recyclée en tête de procédé. Puis, l’émulsion huile/eau la plus dense pourra être utilisée pour la formulation de crèmes cosmétiques. Pour sa part, la phase hydrophobe supérieure sera utilisable pour le traitement de surface des agromatériaux par enduction afin de les rendre moins sensibles à l’eau. Sa démixtion facilitera également l’obtention de protéines tensioactives, utilisables dans l’industrie alimentaire. Enfin, le tourteau étant un mélange de protéines plastifiées et de fibres, il a été considéré comme un composite naturel, moulable en panneaux de fibres cohésifs par thermopressage ou par moulage par compression. Les panneaux auto-liés de haute densité pourront être utilisés comme des panneaux travaillants, utilisés en milieu sec (sous-couches pour le sol, cloisons intérieures, meubles, etc.). Positionnés dans les murs et les plafonds, les panneaux de densité moyenne ou faible pourront servir à l’isolation thermique des bâtiments. Par ailleurs, le tourteau pourra aussi être utilisé comme isolant en vrac. Tel que proposé, ce schéma de procédé permet ainsi une valorisation de toutes les fractions provenant du réacteur bi-vis.

International audience; New thermal insulation fiberboards were manufactured by compression molding from a cake generated during the sunflower biorefinery. Fiberboards were cohesive mixtures of a natural binder and lignocellulosic fibers from sunflower cake. The natural binder ensured the board cohesion, and fibers acted as reinforcing fillers. The influence of molding conditions, i.e. binder type and binder content, on board density, mechanical and heat insulation properties was examined. The medium-density board containing 20% starch-based binder was a good compromise between mechanical and heat insulation properties (78 mW/m K thermal conductivity). It could be positioned on walls and ceilings for thermal insulation of buildings.

International audience; The objective of this study was to manufacture new biodegradable fiberboards by thermo-pressing. The starting material was deoiled cake (only 0.9% oil content), generated during the biorefinery of sunflower (Helianthus annuus L.) whole plant in a co-rotating twin-screw extruder. All fiberboards were cohesive mixtures of proteins and lignocellulosic fibers, acting respectively as binder and reinforcing fillers. The molding experiments were conducted using a 400 ton capacity heated hydraulic press. The influence of molding conditions on board density, mechanical and thermo-mechanical properties, thickness swelling, and water absorption was examined. Molding conditions included pressure applied (24.5–49.0 MPa), molding time (60–300 s), and mold temperature (156–204◦C), and these greatly affected board density and thus the mechanical and thermo-mechanical properties. Board density increased with increasingly extreme molding conditions, rising from 1162 to 1324 kg/m3. The flexural properties increased at the same time (from 12.2 to 27.7 MPa for flexural strength at break, and from 2183 to 5244 MPa for elastic modulus) and also Shore D surface hardness (from 69.6 to 79.0◦). Conversely, Charpy impact strength was low and quite independent of thermo-pressing conditions. Statistical analysis of the Doehlert’s experimental design was conducted to determine optimal thermo-pressing conditions for flexural properties, giving 49.0 MPa pressure applied, 300 s molding time, and 204◦C mold temperature. Density of boards molded under these conditions was 1267 kg/m3. Flexural strength at break, elastic modulus and Shore D surface hardness were 30.3 MPa, 5946 MPa, and 81.5◦, respectively, and these corresponded to the highest values for the entire study. Such boards largely complied with French standard NF EN 312, type P4 (i.e. load bearing boards for use in dry conditions) for flexural properties. However, thickness swelling (30%) needs to be slightly reduced to achieve the 21% recommended standard value.

International audience; Are nettle fibres produced on metal-contaminated lands suitable for composite applications ?