Properties of Modified Wood According to Treatment Technology and Thermo-Vacuum Process for Birch (Betula pendula Roth) Veneers

Thermally modified birch (Betula pendula Roth) veneers that had been subjected to wood treatment technology (VVTT) or thermo vacuum (TV) processes were compared in this study. After modification of veneers in the range of temperatures from 160 degrees C to 218 degrees C and times from 0.5 h to 3 h, the color, mass loss, density, tensile strength, hygroscopicity, and decay resistance against brown rot fungus Coniophora puteana were determined. Treatment regimes with the greatest mass loss were at 217 degrees C for 3.0 h in TV (7.8%) and 160 degrees C for 0.8 h in the VVTT (6.7%). As expected, wood mass loss correlated well with moisture exclusion efficiency (MEE) in all relative humidity (RH) environments (r = 0.95 to 0.99). Strength loss in the VVTT was considerable compared to the TV process (57% and 40%, respectively). The resistance against brown rot fungus was moderate with a mass loss of 12% to 33%. Among the investigated samples, the regime 217/3.0/TV showed the best resistance against brown rot fungus and acceptable other properties.