Southern pine methyl isocyanate reaction

In a study concerned with the decay resistance provided by isocyanate bonding to wood, the distribution of the methyl isocyanate reaction in southern pine showed that 60% of the lignin hydroxyls and 12% of the holocellulose hydroxyls are substituted at the point where resistance to biological attack occurs. Therefore, it can be surmised that the chemical bonding of wood by isocyanates through the urethane link can contribute significantly to the excellent performance of diphenylmethane-diisocyanate X or polymeric isocyanates XI as adhesive binder in particle boards (24, 25). 

Rowell, R.M. and Ellis, W.D. (1979). Chemical modification of wood reaction of methyl isocyanate with southern pine. Wood Science, 12(1), 52-58. 

In the reaction of wood hydroxyls with isocyanates, a nitrogen-containing ester is formed. A limited reduction of fungal attack was reported earlier in beechwood modified with diisocyanate (13). Considerably more decay protection than acetylation has been shown in the methyl and allyl isocyanate modifications. Little decay was evident in methyl isocyanate-modified southern pine at WPGs between 14% and 19% in laboratory assay using G. trabeum. 

Evidence that chemical reaction has taken place with wood cell wall hydroxyl groups is evident from the infrared (IR) spectra of methyl isocyanate-modified southern pine (Figure 3). All samples run in the IR were first milled to pass a 40-mesh screen and extracted first with benzene/ethanol (2/1, v/v) followed by water in a Soxhlet extractor. Any unreacted reagent and isocyanate homopolymer formed during the reaction with wood would be removed by this extraction procedure. The spectrum for unreacted... 

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