How to decrease the hydrophilicity of wood flour to process efficient composite materials

Dynamic fluorination and static fluorination were applied to wood flour to decrease its hydrophilic character, aiming at processing wood-polymer composites with good properties. Fourier-Transform infrared spectra and F-19 solid state NMR (Nuclear Magnetic Resonance) results proved the successful covalent bonding of fluorine atoms onto the wood's chemical structure. It revealed that static fluorination brings about a less damaged and less hydrophilic fluorinated wood than with dynamic fluorination. Composites manufactured from this fluorinated wood presented a hydrophobic character directly related to the hydrophicity of these wood reinforcements. A composite made with fluorinated wood and polyester exhibited a higher hydrophobicity than the neat polyester and than the composite made with nontreated wood. Moreover, the further fluorination of a composite made of fluorinated wood led to a contact angle comparable to that of some metals (steel, gold) due to the etching of the composite surface during fluorination. (C) 2015 Elsevier B.V. All rights reserved.