Effect of press-drying on static bending properties of plantation-grown No. 2 loblolly pine lumber.
Authors:
Stoker, D.L. Pearson, R.G. Kretschmann, D.E. Tang, Y. Simpson, B. USDA, FS
Source:
Forest products journal. 2007 Nov., v. 57, no. 11, p. 70-73.
NALT Subjects:
lumber wood defects wood drying Pinus taeda juvenile wood plantation forestry temperature pressure modulus of rupture modulus of elasticity loads specific gravity bending strength lumber grades
Other Subjects:
warp
Issue Date:
Nov-2007
Abstract:
The purpose of this study was to determine the effects of two press-drying treatments on the static bending properties of plantation-grown, No. 2 grade, 2 by 4 loblolly pine lumber. Specimens were divided into groups containing primarily juvenile wood or primarily mature wood. The groups were subjected to three drying method-temperature/pressure combinations: (1) kiln-drying at 116 degrees C (240 degrees), (2) press-drying at 172 or 345 kPa (25 or 50 psi), and (3) press-drying at 177 or 210 degrees C (350 or 410 degrees). Modulus of rupture (MOR), modulus of elasticity (MOE), work to maximum load (WML), and specific gravity (SG) were determined. The results showed no change in SG in relationship to press-dry treatment and no practical differences in both MOE and MOR between press-dried and kiln-dried specimens. The only significant change was a decrease in work to maximum load with press-drying at 345 kPa and 210 degrees C (50 psi and 410 degrees), which was detectable only in the higher quality pieces. The results suggest that loblolly pine properties are far more affected by the presence of juvenile wood and the inherent defects associated with the No. 2 grade than by press-dry treatment. Further work is needed to determine the influence of press-drying on the SG of full-size lumber. We expect that any effects will be most noticeable in higher quality pieces.
