Elaboration of hydrophobic flax fibers through fluorine plasma treatment

International audience; In this study, the goal was to compatibilize flax natural fibers (which are inherently polar) with mostly dispersive polymers, while proposing a way to recover greenhouse gases or refrigerants such as CF4 or C2F5H. Such gases exhibit a high global warming potentials (GWPs) and their recovery at the end of their lifecycle is difficult. Therefore, these two representative problematic gases were used as plasma precursor to graft fluorine atoms onto the flax fiber surface. Chemical investigation (FT-IR, 19F NMR and XPS spectroscopies), demonstrates the covalent grafting of fluorine atoms at the fiber surface, that opens the route of tailoring the surface chemistry of flax fibers. These modifications induced a decrease of the fiber polarity, which allows the treated fibers to become perfectly compatible with mostly dispersive polymer. Moreover, both mechanical properties and fluorine release during fibers combustion were investigated and any negative impact was evidenced. Therefore, thanks to the plasma fluorination, the gap between the surface energies of the fibers and mostly dispersive polymer matrix was reduced improving the wettability of the fibers through an eco-friendly way. This phenomenon promising an improvement in the mechanical performance of eco-composites reinforced with these fluorinated fibers.