Analysis of water vapour sorption of oleo-thermal modified wood of Acacia mangium and Endospermum malaccense by a parallel exponential kinetics model and according to the Hailwood-Horrobin model

Two Malaysian hardwoods, acacia (Acacia mangium Wild.) and sesendok (Endospermum malaccense Bent. ex Mull. Arg.) that had been previously subjected to oleo-thermal modification, were studied to determine their dynamic sorption kinetic behaviour. All specimens were thermally modified in palm oil at 180 degrees C, 200 degrees C, and 220 degrees C and 3 h treatment time. Data were analysed using the parallel exponential kinetics (PEK) model, and excellent fits to the experimental data were obtained. The relation between the monolayer water and polylayer water was also examined by the Hailwood-Horrobin (H-H) model at a range of relative humidity (RH) values. The PEK model divides the sorption kinetics curve into a fast and slow sorption processes. Characteristic times of the two processes at various RH showed sorption hysteresis with all of the specimens only in the slow process. However, with mass change data, sorption hysteresis occurred with both the slow and fast processes. By comparing H-H and PEK models, it was found that the fast and slow sorption process of untreated and treated E. malaccense could possibly be linked, respectively, to monolayer and polylayer formation from 5 to 40% RH. No such correlation was found for A. mangium, however.