By utilizing corona-pretreatment, wood-polymer composite (WPC) was made with styrene monomer and hinoki (Chamaecyparis obtusa End1.), and its dimensional stability was investigated.
The wall polymer produced was 7% at a maximum, showing a very low value compared with that of MMA (methyl methacrylate)-WPC made by both corona discharge and heat-catalyzed method which were reported previously.The ASE（antiswelling efficiency) of styrene-WPC under moisture absorption showed roughly 20-38% except for the WPC made at a monomer concentration of 1OO%, and it was not much different from the case of MMA-WPC. The ASE and MEE (moisture-excluding efficiency）were directly proportional to the wall polymer content. So it is clear that in styrene-WPC the dimensional stability was greatly improved by the presence of a small amount of wall polymer. But the wall polymer did not have much effect on the ASE under water absorptionand the WEE (water-excluding efficiency).
Less polymer produced by corona discharge in styrene-WPC seems to be due to styrene being harder to polymerize radically compared with MMA so that little polymer was observed in the cell lumina of styrene-WPC. The presence of a little wall polymer is assumed to be restricted to only the vicinity of the intercellular layer. For improving more greatly the dimensional stability of styrene-WPC against moisture absorption as well as water absorption, treatment to make polymer exist in the whole cell walls including the secondary wall would be required.