The effect of species and species distribution on the layer characteristics of OSB.

Southern pine and aspen are widely utilized species for oriented strandboard (OSB) production in North America. In general, aspen with a relatively low specific gravity and uniform cell structure arrangement is considered more suitable for composite panel manufacture than is southern pine. Aspen OSB typically is lower in density and has better dimensional stability when compared to pine OSB. The purpose of this study was to investigate the effects of species use and distribution within OSB panels on the formation of the vertical density profile, resulting layer thickness swelling, and end-product layer characteristics. Five species configurations were used in this study (by weight): all pine, all aspen, 50/50 percent mixture, 25 percent aspen faces/50 percent pine core, and 25 percent pine faces/50 percent aspen core. Results show that the shape of the vertical density profile was considerably affected by species and species distribution. Resulting shapes of the vertical density profile were described as steep or gradual, referring to the densification of the face layers relative to the core. A steep profile has high density surface layers relative to the core and a gradual profile exhibits less difference between the face and core layers. The face density region of the density profile was further described as either a narrow density peak or a wide density peak, referring to the degree of density change within the face itself. The all-aspen panel had a steep density profile with a very narrow density peak. The 25 percent pine faces/50 percent aspen core panel had a more gradual density profile with a wide density peak. There was a strong relationship between layer density and layer thickness swelling. Physical and strength properties for all species combinations of panel types are reported.