Fluorination renders the wood surface hydrophobic without any loss of physical and mechanical properties
Résumé
he main limiting factor for the use of solid wood lies in its highly hydrophilic character which is associated with the loss of its properties after moisture uptake. Therefore for limiting the negative impact of moisture in wooden structures, numerous research have been carried out in order to (i) protect the surface of wood by the addition of varied varnish or protections or to (ii) modify the wooden surfaces structure by the mean of different technologies such as thermal treatments.The former present the disadvantage to protect the wood surfaces for a limited period of time while the later present the disadvantage to reduce the mechanical properties.The aim was investigate how to reduce the hydrophilic character of wood without reducing physical and/ mechanical properties.We use dynamic fluorination using F-2 gas applied to wood samples (Douglas and silver fir) for reducing the hydrophilic character.The covalent grafting of fluorine atoms on a wood surface was highlighted by Fourier-Transform infrared spectroscopy and F-19 solid state Nuclear Magnetic Resonance. The wood samples acquire a hydrophobic character comparable to that of Polytetrafluoroethylene, thanks to fluorination. The high durability of this treatment was also determined by aging tests under ambient atmosphere and UV irradiation. Moreover, this treatment gives a surface with a hydrophobic character without major structural (morphology, density and colour) and mechanical modifications.Maintaining those properties after fluorination, a dried gas/solid treatment without the use of toxic solvents and high temperatures seems to show a remarkable advantage over other physical chemical wood treatments.
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