In this paper, the effects of some plasticizers on the bending behavior for wood -plastic combination (WPC) which was prepared with methyl methacrylate (MMA)-plasticizer system were investigated. Eight species used in this experiment were Sugi (Cryptomeria japonica D. Don), Hinoki (Chamaecyparis obtusa Endl.), Kuromatsu (Pinus thunbergii Parl.), Akamatsu (Pinus densiflora Sieb. et Zucc.), Karamatsu (Larix leptolepis Gordon), Douglas-fir (Pseudotsuga menziesii Franco), Makanba (Betula maximowiczii Regel) and Yellow seraya (Shorea faguetiana Heim). The additions to MMA were dimethyl phthalate (DMP), dibutyl phthalate (DBP), dioctyl phthalate (DOP) and butyl benzyl phthalate (BBP) as plasticizers, and polyethylene glycol 400 (PEG).
The results of this experiment are as follows :
1) The polymer contents of WPC which were prepared with MMA-plasticizer system and MMA only were almost equal.
2) The modulus of rupture in bending and the absorbed energy in impact bending on WPC increased 1.5 to 3.0 times than those in untreated wood with a few exceptions. But the modulus of elasticity in bending on WPC increased only slightly over that in untreated wood, except for Hinoki.
3) There were no significant effects of plasticizers on the bending behaviors for WPC which was prepared with the solution of MMA and plasticizer in the ratio of 10 : 1 volume.
4) Even if the included BBP content into WPC increased, the modulus of rupture in bending on WPC hardly increased. On the other hand, the absorbed energy in impact bending on Akamatsu- and Makanba-WPC increased along with the increased content of BBP.
5) The increased ratio of bending behavior of WPC to that in untreated wood accompanying the increased polymer content was a small quantity, and the modulus of elasticity in bending on WPC decreased occasionally than that in untreated wood.