Influence of the chemical modification of the interface on the dispersion of lignocellulosic reinforcements in Green Wood Plastic Composites GWPC : numerical model contribution on the optimization of the mechanical properties

Cette étude se concentre sur les « Green Wood Plastic Composites » (GWPC) élaborés avec des matrices de type polyesters aliphatiques biodégradables tels que le poly(-caprolactone) PCL, le poly(acide lactique) PLA et le poly(3-hydroxybutyrate-co-3-hydroxyvalérate) PHBHV renforcées par des fibres de Miscanthus giganteus. Afin d’améliorer l‘adhésion entre les fibres végétales et les matrices thermoplastiques, une modification chimique des fibres a été mise au point. Il s’agit de greffer des chaînes de polyesters, de même nature que la matrice, à la surface des fibres végétales, en utilisant la réactivité des doubles liaisons de la lignine par des réactions de type thiol-ène. Comme ces doubles liaisons sont peu nombreuses un agent polyfonctionnel, un polythiol, a été utilisé. Ce type de greffage a permis d’obtenir une réelle augmentation des propriétés mécaniques des composites à base de PCL et de PHBHV. Différentes techniques de mise en œuvre, extrusion, mélangeage, compression et extrusion réactive ont été utilisés afin d’étudier leur influence sur les comportements mécaniques des biocomposites. L'effet de la teneur en fibres, de leur taille et de leur disposition dans la matrice ont été étudiés. Différents modèles analytiques et numériques ont été mis en œuvre pour déterminer le comportement mécanique effectif des biocomposites. Cette étude suggère que le modèle de Mori-Tanaka avec des fibres sous forme d'inclusions cylindriques constitue une bonne approximation du comportement mécanique réel des matériaux. L'utilisation de modèles à éléments finis (FE) a révélé que la transmission de la contrainte appliquée est plus efficace dans le cas de composites à fibres courtes et que les modèles 3D sont plus réalistes que les 2D correspondants. Les modèles mathématiques mis en œuvre et concernant le processus d'extrusion réactive, responsable du greffage du polymère mais également de sa réticulation semblent pouvoir estimer la fraction de la matrice réticulée. Les composites à base de PLA présentent un module d’Young comparable aux composites réalisés avec le poly(propylène) et une bonne résistance dans des conditions de vieillissement peu agressives. L'interdisciplinarité de ce travail basé sur l'association systématique des modèles numériques à la réalisation des biocomposites est une approche complète pour cerner les propriétés de ces matériauxThis study focuses on the Green Wood Plastic Composites (GWPC), manufactured using biodegradable aliphatic polyesters as matrixes, like poly(ε-caprolactone) (PCL), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(lactic acid) (PLA) reinforced with Miscanthus giganteus fibers. In order to improve the adhesion between the thermoplastic matrixes and the vegetal fibers, a chemical treatment of these last was developed. The grafting of polyesters chains of the same nature as the matrix, was carried out on the surface of vegetal fibers, using the reactivity of unsaturated bonds present in the lignin structure through the use of the thiol-ene reaction. As these double bonds are few a polyfunctional agent, a polythiol, was used. This type of grafting allowed to obtain a real increase in the mechanical properties of biocomposites realized with PCL and PHBHV. Various manufacturing techniques such as extrusion, mixing, injection, compression molding and reactive extrusion were used to study their influence on the mechanical behavior of biocomposites. The effect of fibers content, sizes and arrangement in the matrix were also studied. Different analytical and numerical models were implemented to determine the effective mechanical behavior of the biocomposites. This study suggests that a Mori-Tanaka model with fibers as cylindrical inclusions constitutes a good approximation of the real mechanical behavior of the biocomposites. The use of finite element (FE) models revealed that the transmission of the applied stress is more efficient in the case of composites with short fibers and that 3D FE models are more realistic than their corresponding 2D. Mathematical models here implemented concerning the reactive extrusion process, this last being responsible not only of the polymer grafting but also of the polymer cross-linking, seem to be able to estimate the fraction of cross-linked matrix. PLA-based composites exhibit a Young Modulus comparable to their equivalent realized with poly(propylene), showing also a good resistance to mild aging conditions. The interdisciplinarity of this work based on the systematic association of numerical models to the practical realization of the biocomposites constitutes a complete approach to determine the properties of these material

Influence de la modification chimique de l’interface sur la dispersion des renforts lignocellulosiques dans les Green Wood Plastic Composites (GWPC) : apport de la modélisation sur l’optimisation des propriétés mécaniques

This study focuses on the Green Wood Plastic Composites (GWPC), manufactured using biodegradable aliphatic polyesters as matrixes, like poly(ε-caprolactone) (PCL), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and poly(lactic acid) (PLA) reinforced with Miscanthus giganteus fibers. In order to improve the adhesion between the thermoplastic matrixes and the vegetal fibers, a chemical treatment of these last was developed. The grafting of polyesters chains of the same nature as the matrix, was carried out on the surface of vegetal fibers, using the reactivity of unsaturated bonds present in the lignin structure through the use of the thiol-ene reaction. As these double bonds are few a polyfunctional agent, a polythiol, was used. This type of grafting allowed to obtain a real increase in the mechanical properties of biocomposites realized with PCL and PHBHV. Various manufacturing techniques such as extrusion, mixing, injection, compression molding and reactive extrusion were used to study their influence on the mechanical behavior of biocomposites. The effect of fibers content, sizes and arrangement in the matrix were also studied. Different analytical and numerical models were implemented to determine the effective mechanical behavior of the biocomposites. This study suggests that a Mori-Tanaka model with fibers as cylindrical inclusions constitutes a good approximation of the real mechanical behavior of the biocomposites. The use of finite element (FE) models revealed that the transmission of the applied stress is more efficient in the case of composites with short fibers and that 3D FE models are more realistic than their corresponding 2D. Mathematical models here implemented concerning the reactive extrusion process, this last being responsible not only of the polymer grafting but also of the polymer cross-linking, seem to be able to estimate the fraction of cross-linked matrix. PLA-based composites exhibit a Young Modulus comparable to their equivalent realized with poly(propylene), showing also a good resistance to mild aging conditions. The interdisciplinarity of this work based on the systematic association of numerical models to the practical realization of the biocomposites constitutes a complete approach to determine the properties of these materialsCette étude se concentre sur les « Green Wood Plastic Composites » (GWPC) élaborés avec des matrices de type polyesters aliphatiques biodégradables tels que le poly(-caprolactone) PCL, le poly(acide lactique) PLA et le poly(3-hydroxybutyrate-co-3-hydroxyvalérate) PHBHV renforcées par des fibres de Miscanthus giganteus. Afin d’améliorer l‘adhésion entre les fibres végétales et les matrices thermoplastiques, une modification chimique des fibres a été mise au point. Il s’agit de greffer des chaînes de polyesters, de même nature que la matrice, à la surface des fibres végétales, en utilisant la réactivité des doubles liaisons de la lignine par des réactions de type thiol-ène. Comme ces doubles liaisons sont peu nombreuses un agent polyfonctionnel, un polythiol, a été utilisé. Ce type de greffage a permis d’obtenir une réelle augmentation des propriétés mécaniques des composites à base de PCL et de PHBHV. Différentes techniques de mise en œuvre, extrusion, mélangeage, compression et extrusion réactive ont été utilisés afin d’étudier leur influence sur les comportements mécaniques des biocomposites. L'effet de la teneur en fibres, de leur taille et de leur disposition dans la matrice ont été étudiés. Différents modèles analytiques et numériques ont été mis en œuvre pour déterminer le comportement mécanique effectif des biocomposites. Cette étude suggère que le modèle de Mori-Tanaka avec des fibres sous forme d'inclusions cylindriques constitue une bonne approximation du comportement mécanique réel des matériaux. L'utilisation de modèles à éléments finis (FE) a révélé que la transmission de la contrainte appliquée est plus efficace dans le cas de composites à fibres courtes et que les modèles 3D sont plus réalistes que les 2D correspondants. Les modèles mathématiques mis en œuvre et concernant le processus d'extrusion réactive, responsable du greffage du polymère mais également de sa réticulation semblent pouvoir estimer la fraction de la matrice réticulée. Les composites à base de PLA présentent un module d’Young comparable aux composites réalisés avec le poly(propylène) et une bonne résistance dans des conditions de vieillissement peu agressives. L'interdisciplinarité de ce travail basé sur l'association systématique des modèles numériques à la réalisation des biocomposites est une approche complète pour cerner les propriétés de ces matériau

Effect of Miscanthus Giganteus on PHBHV matrix: numerical modeling contribution on the evaluation of the mechanical properties

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Effect of Miscanthus Giganteus on PHBHV matrix: numerical modeling contribution on the evaluation of the mechanical properties

International audienc

Effect of Miscanthus Giganteus modification on the interface matrix/reinforcement in the Green Wood Plastic Composites: numerical modeling contribution on the optimization of the mechanical properties.

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Effect of Miscanthus Giganteus modification on the interface matrix/reinforcement in the Green Wood Plastic Composites: numerical modeling contribution on the optimization of the mechanical properties.

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Biocomposites Based on Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate) (PHBHV) and Miscanthus giganteus Fibers with Improved Fiber/Matrix Interface

In this paper, green biocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) and Miscanthus giganteus fibers (MIS) were prepared in the presence of dicumyl peroxide (DCP) via reactive extrusion. The objective of this study was to optimize the interfacial adhesion between the reinforcement and the matrix, improving the mechanical properties of the final material. To this aim, two fibers mass fractions (5 and 20 wt %) and two different fiber sizes obtained by two opening mesh sieves (1 mm and 45 μm) were investigated. The impregnation of fibers with DCP before processing was carried out in order to promote the PHBHV grafting onto MIS fibers during the process, favoring, in this way, the interfacial adhesion between fibers and matrix, instead of the crosslinking of the matrix. All composites were realized by extrusion and injection molding processing and then characterized by tensile tests, FTIR-ATR, SEM, DSC and XRD. According to the improved adhesion of fibers to matrix due to DCP, we carried out an implementation of models involving that can predict the effective mechanical properties of the biocomposites. Three phases were taken into account here: fibers, gel (crosslinked matrix), and matrix fractions. Due to the complexity of the system (matrix–crosslinked matrix–fibers) and to the lack of knowledge about all the phenomena occurring during the reactive extrusion, a mathematical approach was considered in order to obtain information about the modulus of the crosslinked matrix and its fraction in the composites. This study aims to estimate these last values, and to clarify the effect caused by the presence of vegetal fibers in a composite in which different reactions are promoted by DCP

Study of Mechanical Properties of PHBHV/Miscanthus Green Composites Using Combined Experimental and Micromechanical Approaches

International audienceIn recent years the interest in the realization of green wood plastic composites (GWPC) materials has increased due to the necessity of reducing the proliferation of synthetic plastics. In this work, we study a specific class of GWPCs from its synthesis to the characterization of its mechanical properties. These properties are related to the underlying microstructure using both experimental and modeling approaches. Different contents of Miscanthus giganteus fibers, at 5, 10, 20, 30 weight percent’s, were thus combined to a microbial matrix, namely poly (3-hydroxybutyrate)-co-poly(3-hydroxyvalerate) (PHBHV). The samples were manufactured by extrusion and injection molding processing. The obtained samples were then characterized by cyclic-tensile tests, pycnometer testing, differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray diffraction, and microscopy. The possible effect of the fabrication process on the fibers size is also checked. In parallel, the measured properties of the biocomposite were also estimated using a Mori–Tanaka approach to derive the effective behavior of the composite. As expected, the addition of reinforcement to the polymer matrix results in composites with higher Young moduli on the one hand, and lower failure strains and tensile strengths on the other hand (tensile modulus was increased by 100% and tensile strength decreased by 23% when reinforced with 30 wt % of Miscanthus fibers)

Functionalization of Miscanthus by Photoactivated Thiol–Ene Addition to Improve Interfacial Adhesion with Polycaprolactone

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Functionalization of Miscanthus by Photoactivated Thiol–Ene Addition to Improve Interfacial Adhesion with Polycaprolactone

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