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Philippe Tingaut, Oliver Weigenand, Carsten Mai, Holger Militz, Gilles Sèbe
Chemical reaction of alkoxysilane molecules in wood modified with silanol groups
Keywords: alkoxysilanes, 13C and 29Si CP-MAS NMR, chemical modification, FTIR Spectroscopy, SEM-EDX analysis, silanol groups, wood
Chemical reaction between silanol-modified wood and methyltrimethoxysilane (MTMS) was carried out using two different approaches with dibutyltin dilaurate (DBTDL) or ethylamine (EtNH2) as catalysts. Modifications were characterised by Fourier-transform infrared (FTIR) spectroscopy, as well as solid-state 13C and 29Si cross-polarisation with magic-angle spinning nuclear magnetic resonance (CP-MAS NMR) spectroscopy and scanning electron microscopy-energy dispersive X-ray (SEM-EDX) analysis. Silanol-modified wood was obtained by carbamoylation reaction with 3-isocyanatopropyltriethoxysilane (IPTES) and subsequent hydrolysis of the triethoxysilane end groups. 29Si CP-MAS NMR spectroscopy indicated that SiOH groups existed mostly in the form of mono- and di-condensed structures in wood, whatever the level of modification (low or high). The attachment of methyltrimethoxysilane (MTMS) molecules to silanol sites was apparently achieved when ethylamine was used as a catalyst. The reacted MTMS remaining in wood was found to exist mostly in the form of polysiloxane polymers (or oligomers), as shown by 29Si CP-MAS NMR results. Reactions performed with unmodified wood were much less effective, thereby demonstrating the importance of the IPTES pre-treatment.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 60, 05/2006
Pages: 271 - 277