The resistance of wood chemically modified with isocyanates: the role of moisture content in decay suppression

Abstract

This paper discusses the moisture content of sound and decayed Corsican pine (Pinus nigra) after modification with isocyanates {n-butyl isocyanate (BuNCO) and 1,6-diisocyanatehexane (HDI)} at specified intervals of weight percent gain (WPG). The main effects of decay fungi (brown and white rot) and levels of modification (WPG) on moisture contents of modified samples are also examined. Corsican pine reacted with isocyanates enhanced the hydrophobic (restrained water) nature of wood. The equilibrium moisture content of chemically modified wood decreases progressively with increasing WPG. Basidiomycete decay tests demonstrated protection by chemical modification. Wood moisture contents after soil block testing are significantly influenced by decay fungi and by the extent of reaction (WPG). Moisture uptake and susceptibility to decay of modified wood are higher when exposed to Coniophora puteana than other decay fungi. Corsican pine cross-linked by reaction with HDI is less susceptible to decay and is more hydrophobic than samples reacted with the single-site reactant BuNCO at comparable WPG.