The calculation of EMC for the analysis of wood/water relations in Fagus sylvatica L. modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea

Beech wood (Fagus sylvatica L.) was modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU). The equilibrium moisture content (EMC) of wood modified with DMDHEU calculated on a dry modified basis is reduced. Previous results have shown that the modification with DMDHEU does not alter the capillary condensation; therefore, the reduction in EMC seems exaggerated. The equilibrium constants of the Hailwood–Horrobin model (K d and K h) and the molecular weight of a hypothetical polymer of modified wood capable of adsorbing one molecule of water (W i) were calculated from the EMC on a dry modified wood basis (M) and on a dry wood basis (M R). The hypothetical polymer was also calculated by stoichiometry (W c) and compared to W i to estimate the number of operative OH groups. The number of operative OH groups decreased when M was used, in contradiction with the previously obtained results of differential heat of adsorption (∆H s). Therefore, the use of M R is recommended for the analysis of moisture sorption in wood modified with DMDHEU.