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Flax fibres modification for the development of biocomposites

Published on February 2, 2021
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PhD Defense December 10, 2020

Estelle Doineau, PhD student of the LGP2, defended her doctoral thesis: "Flax fibres modification by cellulose nanocrystals and xyloglucan for the development of hierarchical biobased composites".

This doctoral thesis from the École Nationale Supérieure des Mines d'Alès (IMT Mines Alès) was prepared under the supervision of Professor Jean-Charles Bénézet (IMT Mines Alès) and Julien Bras, Senior Lecturer HDR (Grenoble INP- Pagora / LGP2), and the co-supervision of Nicolas Le Moigne, Teacher-researcher (IMT Mines Alès) and Bernard Cathala, Research Director, INRAe Nantes.

Estelle Doineau presented the results of her research work entitled Flax fibres modification by cellulose nanocrystals and xyloglucan for the development of hierarchical biobased composites.

This thesis project aims at developing flax fibres surface treatment for the improvement of the mechanical properties of biocomposites with polymeric matrix and flax reinforcements.

This surface modification is inspired by the hierarchical structures present in biological systems (bone, nacre or wood), composed of nano-objects which allow a better transfer of loads in these materials. This presence of nano-sized objects makes it possible to reach impressive strength and toughness values and to limit cracks propagation.

In this project, products derived from lingo-cellulosic biomass, namely cellulose nanocrystals (CNC) and xyloglucan (XG), were chosen for their interesting properties and mutual affinity to create hierarchical flax fibres. In a first step, the adsorption of XG and CNC on flax fibres was localized and quantified using fluorescent markers.  In addition, atomic force microscopy measurements of adhesive force revealed the creation of an extensible XG/CNC network on the fibre surface. Subsequently, two paths were proposed with the elaboration of thermoplastic (polypropylene/flax fibres) and thermoset (epoxy resin/flax fabric) biocomposites using these nanostructured fibres. In both cases, an increase of the work of rupture has been measured by micro- and/or uniaxial tensile tests, allowing dissipating more energy upon breakage.

All this work has allowed evaluating the potential of different hierarchical natural reinforcements (unidirectional fabric or short flax fibers) for the development of structural biocomposites with a focus on the fiber/matrix interphase zone.
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Date of update June 22, 2021

Université Grenoble Alpes