抄録
In order to prepare a wood-polymer composites having dimensional stability and hygroscopicity similar to wood itself, the radical copolymerization of a hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA), with a hydrophobic monomer, methyl methacrylate(MMA), in heartwood of Hinoki (Chamaecyparis obtusa SIEB. et ZUCC.) was investigated. The hygroscopicity and dimensional stability were evaluated by the mole fraction of HEMA in MMA-HEMA system, the moisture content in the wood part and the polymer content in the wood-polymer composite.
The results obtained are as follows:
(1) The hygroscopicity of the wood-polymer composite is improved with increasing mole fraction of HEMA in MMA-HEMA system. At 1.0 of HEMA mole fraction, the moisture-excluding efficiency in the equilibrium state at 20°C and 93% or 75% relative humidity is about 10%.
(2) The anti-swelling efficiency decreases linearly with an increase in mole fraction of HEMA, and above 0.3 of HEMA mole fraction, the dimensional stability cannot be attained. The anti-swelling efficiency is directly proportional to the moisture-excluding efficiency. The dominating factor for dimensional stabilization due to the impregnation of MMA-HEMA copolymer in wood is the bulking effect and reduction of hygroscopic sites in wood components.
(3) The moisture-excluding efficiency is nearly proportional to polymer content. The anti-swelling efficiency changes with polymer content and exhibits a remarkable increase at about 100% of polymer content.
