Abstract
In order to prepare a composite material having dimensional stability and hygroscopicity similar to wood itself, the liquid phase reaction of ethylene glycol (EG) and 4, 4'-diphenylmethane diisocyanate (MDI) with heartwood of Hinoki (Chamaecyparis obtusa SIEB. et ZUCC.) was investigated. The hygroscopicity and dimensional stability were evaluated by the amounts of hydroxyl group and combined urethane which were introduced into wood.
In the reaction of EG and MDI in wood, the nitrogen content and the reactant combined with wood components increased with an increase in mole fraction of MDI in MDI-EG system, but the degree of crystallinity decreased. This shows that the reaction took place somewhat in the crystalline region. The formation of urethane in the treated wood was also identified.
The anti-swelling efficiency (ASE) and moisture-excluding efficiency (MEE) showed the maximum values at about 0.5 of MDI mole fraction in any concentration of solutions. ASE and MEE were 69.3% and 59.4% at 15% concentration, respectively. ASE was directly proportional to the MEE and bulking. When the free EG was removed from the treated wood, ASE and MEE decreased remarkably, and MEE tended to decrease with an increase in ASE. It suggests that free EG considerably affects ASE, MEE and bulking.
