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 (a dagger H (s)). Therefore, the use of M (R) is recommended for the analysis of moisture sorption in wood modified with DMDHEU.