A Theory of Wood Waterproofing by Complexes of Metal Oxides with Lignin Structural Units

Abstract

SYNOPSIS The effect of various metallic oxides and hydroxides on wood waterproofing was investigated. The waterproofing effect was attributed to the type of complexes formed by the metallic oxide with the guaiacol units of the lignin network of wood. The type of structure of the complex formed, as well as its insolubility, contribute to the wood waterproofing, although to a different extent. Only Cr, Zn, Pb and Sn oxides formed insoluble complexes. Of these only Cr and Zn oxides are able to waterproof wood, although to a different extent. This was attributed to their capacity to further cross-link the lignin network in wood, which renders more difficult water penetration and improves wood dimensional stability. While it is necessary for the complexes formed to be insoluble, their insolubility is not the main contributing factor to wood waterproofing and its dimensional stabilisation.