The effects of increasing preservative uptake by microwave pre-treatment on the microstructure and mechanical properties of Oriental spruce wood

In the microwave (MW) pre-treatment process, a constant MW energy intensity of 2158 MJ/m(3) was applied by using 925 W (3700 sec.), 1295 W (2640 sec.) and 1850 W (1850 sec.) powers. Tanalith-E preservative material was used to determine the increase in impregnability of MW pre-treated wood. The mechanical properties of the treated wood specimens were tested to determine the degradation caused by exposure to the MW radiation. Additionally, scanning electron microscope (SEM) was used to determine the changes in wood microstructure with the effect of microwave pre-treatment. According to the impregnations, the average preservative material retention rates increased 62% for the specimens with MW groups, compared to the reference specimens. The mechanical properties of the MW pre-treated specimens decreased by (average) 5% in compression strength, 12% in the bending strength and 16% in the modulus of elasticity. SEM observations of the reference specimens showed that there were many aspirated bordered pits before MW pre-treatment. After the MW pre-treatment, parts of the pit membranes were damaged. The torus ruptured and cracked, while the structure of the micro-fibrils on the margo remained intact. In the observations of the intercellular microstructure of wood, it was observed that micro cracks with a width of 1-10 mu m were formed.