Studies on the preservation of structrual plywood - Part 1: Decay resistance of structural plywood
K Minami, Y Kenjo, S Sugiyama
The weight loss and the decreases in the compression strength and in the modulus of elasticity were measured to determine the decay resistance of structural plywood (lauan). Test pieces (50x25xA mm³) were exposed to the wood destroying fungi (Coriolus versicolor and Coriolellus palustris) for 2-3 or 2-4 months. After exposure, the measurement of the compression strength was carried out on the pieces of different thickness (A = 6,12 and 18 mm) and different fibre direction of the face veneer (0°, 45° and 90° to the long side of the test piece). The results obtained were as follows: 1.: The weight loss was small. The greatest weight loss was 9.4% on decaying by Coriolellus palustris for 4 months. 2.: The decreases in the compression strength and in the modulus of elasticity were greater than the weight loss. On decaying by Coriolellus palustris for 4 months, the ratio of decrease of the compression strength was 75% (6 mm - 0°). 3.: For differences of the thickness and of the fibre direction, the weight loss and the decreases the modulus of elasticity in the compression strength and in the modulus of elasticity showed tendencies in order 0° > 45° > 90° and 6 > 12 > 18 mm. 4.: According to the experiment, the face veneer is liable to be easily attacked by the wood destroying fungi, but the decrease in the compression strength was great. So, the face veneer and the cross section should be protected with preservatives for structural use.