Matériaux ligno-cellulosiques : "Élaboration et caractérisation"

This work aims at developing new ligno-cellulosic biomass based materials as a way for giving added value to this raw material. This study aimed at developing three different new ways of using ligno-cellulosic components to get a large overview of the possible technical materials. The first way deals with the preparation of natural fibres filled lignin fibreboard panels. Improvements in panels forming have been achieved by using either chemical treatment or novel compatibilisation to improve the strength of the prepared fibreboards. In a second way, an original forming process by high pressure has been tested and carried out on cotton fibres in order to produce 3D objects without dissolution/coagulation processes of cellulose. After setting up the forming procedure, effects of process parameters and cotton variety on microstructures and mechanical properties of highly compressed cotton have been studied. Finally, a third way was the study of new nanocomposites made of layered double hydroxide modified by lignin (LDH/LS). Using such nanofillers into thermoplastic starch turned out to be an efficient solution to reinforce mechanical properties with low nanofillers loading. This starch-(LDH/LS) nanocomposite was also blended with polyethylene to increase the bio-content without a degradation of the mechanical properties. This study is an advanced basis for a further development of these three different materials and offers a broad range of applications suitable for the preparation of new technical materials.L'objectif de ce travail est de développer l'utilisation de la biomasse ligno-cellulosique dans le domaine des matériaux. Ce travail explore trois voies différentes d'utilisation de la ligno-cellulose afin de balayer un large spectre de constituants et de matériaux finaux. La première voie concerne l'incorporation de fibres naturelles dans la fabrication de panneaux utilisant la lignine comme adhésif. Des améliorations dans la fabrication de ces panneaux de fibres ont été apportées, par traitement chimique ou ajout de nouveaux compatibilisants, permettant un renforcement des propriétés mécaniques. La seconde voie a consisté à développer un procédé original de mise en forme sous haute pression testé et mis en place sur du coton dans le but d'obtenir des objets tridimensionnels sans étape de dissolution/régénération de la cellulose. Une fois le protocole défini, les effets des paramètres de mise en forme et de la variété de coton sur la microstructure et les propriétés mécaniques des objets en coton compressé ont été étudiés. Enfin, une troisième voie à consisté à élaborer des matériaux nanocomposites à partir d'hydroxydes double lamellaire modifiés par la lignine (HDL/LS). L'utilisation de cette nanocharge dans l'amidon a montré une capacité de renforcement pour un faible taux de charge. Ce composite amidon-(HDL/LS) a ainsi été utilisé avec une matrice polyéthylène afin d'augmenter la part renouvelable de la matrice sans diminuer significativement ses propriétés mécanique. Ce travail permet d'envisager des développements futurs pour ces différents matériaux développés et offre ainsi de nouvelles possibilités d'utilisation de la biomasse ligno-cellulosique dans l'élaboration de matériaux techniques

Ligno-cellulose based materials : "Process forming and Characterization"

L'objectif de ce travail est de développer l'utilisation de la biomasse ligno-cellulosique dans le domaine des matériaux. Ce travail explore trois voies différentes d'utilisation de la ligno-cellulose afin de balayer un large spectre de constituants et de matériaux finaux. La première voie concerne l'incorporation de fibres naturelles dans la fabrication de panneaux utilisant la lignine comme adhésif. Des améliorations dans la fabrication de ces panneaux de fibres ont été apportées, par traitement chimique ou ajout de nouveaux compatibilisants, permettant un renforcement des propriétés mécaniques. La seconde voie a consisté à développer un procédé original de mise en forme sous haute pression testé et mis en place sur du coton dans le but d'obtenir des objets tridimensionnels sans étape de dissolution/régénération de la cellulose. Une fois le protocole défini, les effets des paramètres de mise en forme et de la variété de coton sur la microstructure et les propriétés mécaniques des objets en coton compressé ont été étudiés. Enfin, une troisième voie à consisté à élaborer des matériaux nanocomposites à partir d'hydroxydes double lamellaire modifiés par la lignine (HDL/LS). L'utilisation de cette nanocharge dans l'amidon a montré une capacité de renforcement pour un faible taux de charge. Ce composite amidon-(HDL/LS) a ainsi été utilisé avec une matrice polyéthylène afin d'augmenter la part renouvelable de la matrice sans diminuer significativement ses propriétés mécanique. Ce travail permet d'envisager des développements futurs pour ces différents matériaux développés et offre ainsi de nouvelles possibilités d'utilisation de la biomasse ligno-cellulosique dans l'élaboration de matériaux techniques.This work aims at developing new ligno-cellulosic biomass based materials as a way for giving added value to this raw material. This study aimed at developing three different new ways of using ligno-cellulosic components to get a large overview of the possible technical materials. The first way deals with the preparation of natural fibres filled lignin fibreboard panels. Improvements in panels forming have been achieved by using either chemical treatment or novel compatibilisation to improve the strength of the prepared fibreboards. In a second way, an original forming process by high pressure has been tested and carried out on cotton fibres in order to produce 3D objects without dissolution/coagulation processes of cellulose. After setting up the forming procedure, effects of process parameters and cotton variety on microstructures and mechanical properties of highly compressed cotton have been studied. Finally, a third way was the study of new nanocomposites made of layered double hydroxide modified by lignin (LDH/LS). Using such nanofillers into thermoplastic starch turned out to be an efficient solution to reinforce mechanical properties with low nanofillers loading. This starch-(LDH/LS) nanocomposite was also blended with polyethylene to increase the bio-content without a degradation of the mechanical properties. This study is an advanced basis for a further development of these three different materials and offers a broad range of applications suitable for the preparation of new technical materials

Preparation, processing and properties of lignosulfonate-flax composite boards

International audienceHemp, hay, straw for animal litters, raffia and sisal stems, abaca and jute bleached pulp fibres, miscanthus stems and flax fibres were mixed to lignosulfonate at 70% filler concentration and compressed in the form of 5 cm-thick boards. Flax was found to give the best mechanical properties measured in bending mode and used for all tests. Several methods able to improve adhesion between matrix and flax fibres were studied. A treatment of flax fibres with NaOH-water was found to decrease the mechanical properties of composites. Ethanol or dichloromethane solvents that are known to dewax flax fibre surfaces improve the mechanical properties of final board. The addition of pectin to the lignosulfonate matrix was found to improve the mechanical properties in the same order of magnitude as with the ethanol treatment. Both methods improve the flexural strength by 60% while keeping the elastic modulus constant. Mechanical improvement shows that these two methods are increasing the lignosulfonate/flax fibre interfacial adhesion. The best compositions have mechanical properties above the normalized minimum required for wood-based board

Destructuration of cotton under elevated pressure

International audienceDry and wet cotton linters were compressed under elevated pressure in a home-made Bridgman anvil press designed to reach 2.5 GPa and 180 °C. The structural organisation of cotton was changed under the joint action of temperature and pressure. Cotton having high moisture content shows that only a thin surface layer is partially destructured to a compact mat of nanofibres, while the initial cotton fibres are only deformed inside the sample. For dried cotton, the whole sample undergoes a destructuration into a compact mat of nanometre-sized fibres. The mechanical properties were studied by nano-indentation and dynamic mechanical analysis. Compressed dry cotton has higher modulus (10.3 GPa) than wet cotton (6.8 GPa). We postulate that the transverse elastic modulus of cotton microfibrils is around the value of 10 GPa. This work showed that nano-sized fibrils can also be separated in the solid state without flow, and re-compacted to form a solid object

Preparation and properties of blends composed of lignosulfonated layered double hydroxide/plasticized starch and thermoplastics

International audienceLayered double hydroxide prepared with lignosulfonate (LDH/LS) can be easily dispersed down to the nanometric scale in thermoplastic starch, at concentration of 1 up to 4. wt% of LDH/LS. They can thus be used as a bio-based reinforcing agent of thermoplastic starch. Incorporation of LDH/LS in starch must be done using LDH/LS slurry instead of powder on order to avoid secondary particles aggregation, the water of the paste being used as the starch plasticizer. This reinforced starch was used for preparing a starch-polyolefine composite. LDH/LS-starch nanocomposites were mixed in a random terpolymer of ethylene, butyl acrylate (6%) and maleic anhydride (3%) at concentrations of 20. wt% and 40. wt%. With a 20% loading of (1. wt% LDH/LS in thermoplastic starch), the ternary copolymer is partially bio-based while keeping nearly its original processability and mechanical properties and improving oxygen barrier properties. The use of layered double hydroxides is also removing most odours linked to the lignin phase

Influence of cotton variety on compression and destructuration abilities under elevated pressure

International audienceFourteen cotton samples of various strength, maturity and fineness were compressed in the same conditions at elevated pressure (2.0 GPa) and temperature (120 °C) in a home-made Bridgman anvil press designed to process samples of about 20 mm diameter. The influence of cotton properties to the abilities to be compacted into a solid 3D object was studied by mechanical measurements (nano-indentation and DMA) and scanning electron morphology observations. No influence of maturity ratio was observed. But strength and fineness were important parameters. It was shown that the lower are the mechanical properties of the cotton fibres (low strength or large fineness value), the easier it is to compact them. By observing the morphology of compacted samples, it was shown that compaction is linked to the destructuration of fibres under pressure down to the nanofibrillar level. © 2013 Springer Science+Business Media Dordrech

Lignosulfonate interleaved layered double hydroxide: a novel green organoclay for bio-related polymer.

International audienceNew organic inorganic layered double hydroxide (LDH) organoclays are assembled through coprecipitation with lignosulfonate (LS) interleaved inorganic host structure sheets. The biopolymer is found to accommodate the interlayer space adopting a bilayer molecular arrangement resulting in a basal spacing of 2.54 nm. However the crystallinity of the resulting bio-organoclay is weak, probably due to the difficulty of the inorganic sheets to be built on amorphous polymer chain, the latter inducing low structural ordering. An organoclay of composition Zn2Al/LS is subsequently used as filler in three bio-related polyesters, poly(lactic) acid (PLA), poly(butylene) succinate (PBS) and poly(butylene adipate-co-terephthalate) (PBAT). Melt polymer extrusion using 5 wt.% organoclay loading yields polyester nanocomposite with a nanocomposite structure largely intercalated for both PLA and PBS (Δd (expansion) > 6 nm) while a non miscible structure is obtained for PBAT. The incorporation of hydrophilic Zn2Al/LS platelets decreases the water/polymer contact angle of about 10° for the LDH/LS PBAT composite only. A strong increase of the complex viscosity |η*| is observed for both nanocomposites Zn2Al/LS PLA and PBS compared to the polyester itself. This is explained on the basis of a chain extender behavior of the intercalated Zn2Al/LS platelets towards polymer chains as evidenced on the Cole Cole representation showing an increase of the real viscosity in the low-ω region. In opposition a strong decrease in |η*| is observed for PBAT, underlining a plasticizing effect of the organoclay filler. Comparatively, the thermal stability of PLA is slightly enhanced with an increase of T0.5 value while PBS and PBAT bio-nanocomposites degrade at slightly lower temperature

Projet ANR SATIN-BAKING (2012-2016). Revêtements non adhérents perfluorés. Bilan et perspectives

International audienc

Projet ANR SATIN-BAKING (2012-2016). Revêtements non adhérents perfluorés. Bilan et perspectives

International audienc