Functionalisation of wood by reaction with 3-isocyanatopropyltriethoxysilane: Grafting and hydrolysis of the triethoxysilane end groups

The chemical modification of maritime pine sapwood (Pinus pinaster Soland) with 3-isocyanatopropyltriethoxysilane (IPTES) and its subsequent hydrolysis were investigated. The formation of urethane linkages after the carbamoylation reaction was confirmed by Fourier-transform infrared (FTIR) spectroscopy. The weight percent gain (WPG) obtained was found to be commensurate with the quantity of IPTES in the reagent solution. Swelling measurements combined with scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis showed that the reaction occurred within the wood cell walls. Hydrolysis of the grafted triethoxysilane ends in highly carbamoylated wood was also envisaged: the modifications generated after prolonged contact with water were studied by FTIR spectroscopy and 13C and 29Si nuclear magnetic resonance cross-polarisation with magic-angle spinning (NMR CP MAS) analysis. The chemical environments found for silicon (Si–OH, Si–OEt or Si–OSi) before and after hydrolysis were thus identified and a schematic representation of the silicon structures most often encountered in modified wood was proposed.