官能性オリゴマーとメタクリル酸メチルによる木材の寸法安定化
1983 年 32 巻 359 号 p. 904-909
詳細
1983 年 32 巻 359 号 p. 904-909
In order to prepare a wood-polymer composite (WPC) having dimensional stability and hygroscopicity similar to wood itself, the radical copolymerization of a hydrophilic oligomer, polyoxy ethylene glycol monomethacrylate (PEGMA), with a hydrophobic monomer, methyl methacrylate (MMA), in the presence of n-dodecyl mercaptan (RSH) as a chain transfer agent, in heartwood of Hinoki (Chamaecyparis obtusa Sieb, et Zucc.) was investigated. The hygroscopicity and dimensional stability were evaluated on the basis of the mole fraction of PEGMA and concentration of RSH in MMA-PEGMA system, bulking effect and the moisture content in the wood part in WPC.
The results obtained are as follows:
(1) An approximately linear relationship existed between the moisture absorption and the square root of absorption time in the early stage of moisture absorption tests. The retardating efficiency in moisture absorption decreased with increasing mole fraction of PEGMA in MMA-PEGMA system, and above 0.2 of PEGMA mole fraction, the hygroscopicity of WPC was greater than that of untreated wood. The dimensional stability could not be attained for WPC prepared without RSH, while the addition of 1% of RSH in MMA-PEGMA system provided the retardating efficiency in swelling. The anti-swelling efficiency in the equilibrium state at 20°C and 93% relative humidity increased with increasing the concentration of RSH.
(2) The dominating factors for dimensional stability were the bulking effect and reduction of hygroscopic sites in wood components due to the impregnation of MMA-PEGMA copolymer, and the tangential swelling (Y) of WPC could be expressed experimentally as
Y=1.98-0.67X+0.33Z
where X is the bulking effect and Z is the moisture content in the wood part in WPC.
(3) The effective surface area that can absorb moisture in WPC did not change during the absorption and desorption cyclic test. The dimensional stability of WPC prepared in the presence of 1% of RSH remained unchanged in the cyclic tests in the range of 0 to 93% relative humidity and 20°C.
