Résumé
In light of current environmental issues and the emerging context of bio-economy aimed atcontinuing economic growth while preserving the environment and earth resources, vegetal fibers areincreasingly used to substitute glass fibers for polymer strengthening to make eco-composites. Indeed,the use of natural fibers allows bio-based and local resources to be valorized while lightening the overallweight and reducing the cost of composites.Flax fibers are usually considered as adequate bio-reinforcements for composites. However, theirhydrophilic character makes them sensitive to moisture sorption and difficult to wet by hydrophobicresins. This incompatibility can induce a defective interface and micro-porosity between fibers andmatrix that would greatly weaken the eco-composite’s mechanical performance[1][2][3]. Several wayshave been explored to improve wettability of bio-based reinforcements towards resins. However, thesetechniques can damage the initial material and/or are generally harmful to the environment through theuse of toxic products and solvents, which is against the idea of making environmental friendly eco-composites.It is in this context that fluorination treatment takes place. Indeed, a fast and controlled reactiontreatment under molecular fluorine (F2 ) of wood[4] or vegetal fibers allows fluorine atoms to becovalently grafted on the outmost surface of lignocellulosic material in substitution of hydroxyl groupsresponsible for hydrophilicity. This grafting, achieved on flax fibers, allowed the fibers’ polarity to besignificantly decreased without modification of their bulk’s mechanical performance. This reduce thegap between the surface energies of the fibers and different polymer matrix (bio-based epoxy andElium®). In other words, the wetting of the fiber by the polymer is improved during the infusion process.Thereby, porosity into the composite thus formed is significantly reduced, increasing its mechanicalperformance, its health, and its life span during a humid environment aging, without any chemicalcoupling agent harmful to the environment [3][5].[1] F. M. AL-Oqla, M. S. Salit, Materials Selection for Natural Fiber Composites, 2017, 23-48[2] P.-J. Liotier, M.F. Pucci, A. Le Duigou, A. Kervoelen, J. Tirilló, F. Sarasini, S. Drapier, Compos. B.Eng. 163, 2019, 86–95.[3] M.F. Pucci, P.-J. Liotier, D. Seveno, C. Fuentes, A. Van Vuure, S. Drapier, Compos. A: Appl. Sci.Manuf. 97, 2017, 31–40.[4] M. Pouzet, M. Dubois, K. Charlet, A. Béakou, J.-M. Leban, M. Bada, 133, 2019, 133–141.[5] F. Saulnier, M. Dubois, K. Charlet, L. Frezet, A. Beakou, Carbohydr. Polym. 94, 2013, 642–646.