Hiroshi Saotome

Effects of Outdoor Exposure Angle on the Deterioration of Wood-Based Board Properties

Abstract Wood-based boards were exposed to an outdoor environment at angles of 90° and 45° to the ground surface in order to investigate the effect of exposure angle on board properties. In a study on 5-year outdoor exposure, the effects of the exposure angle varied depending on the type of board. Particleboard (PB) and oriented strand board (OSB) deteriorated faster when exposed at 45° compared with 90°, and the difference was more apparent with longer exposure. Five years of exposure at 45° lowered the retention of the modulus of rupture and internal bond of phenolic resin–bonded PB to 15 and 4 percent, respectively. In contrast, medium-density fiberboard (MDF) showed no difference in deterioration between both exposure angles. After 5 years of exposure, the retention of the modulus of rupture was 70 to 80 percent in MDF, while that of internal bond was 81 to 97 percent, thereby showing that the internal bond was better retained than the modulus of rupture. The high durability of MDF was attributable pa...

Improvement of dimensional stability and weatherability of composite board made from water-vapor-exploded wood elements by liquefied wood resin impregnation.

High-density and high-resin-content boards were produced by phenolic resin impregnation into board materials prepared by the water-vapor-explosion process (WVE) to develop high-durability wood composite boards for exterior use. Wet-dry cyclic tests and accelerated weathering tests were conducted, and the fundamental properties were determined to examine the effect of resin impregnation on board qualities. Bending and internal bond strength of resin-impregnated boards (I-board) satisfied the criterion for 18-type particleboard described in JIS A 5908. Thickness swelling (TS) after 24-h water immersion was approximately 2%. Resin impregnation improved the dimensional stability of the boards. In wet—dry cyclic testing, TS of I-board was the same as that of plywood. The retention ratio of modulus of rupture of I-board was large; thus, I-board had high bond durability. Color change of I-board was less than that of ordinary particleboard after a 500-h accelerated weathering test. I-Board had lower surface roughness than boards produced by a spray application method (S-board) and higher water repellency, although the difference in resin contents of the face layer was small. Thus, it is suggested that the surface properties and weatherability of I-board were improved by impregnation of phenolic resin. High-density and resin-impregnated boards made from the WVE elements are expected to withstand actual exterior use.