STRENGTH PROPERTIES OF BLACK SPRUCE WOOD UNDER DIFFERENT TREATMENT

The effect of various forms of treatment - chemical, thermal and press ure on the tensile properties of wood was investigated. Spruce was imp regnated in water, sodium sulfite and/or sodium bicarbonate, and heate d at temperatures ranging from 20 to 190 degrees C. At the end of cook ing (190 degrees C), decompression was applied both slowly and suddenl y. A rise in temperature, an increase in heating time, from 4 to 10 mi n. at 190 degrees C, as well as fast pressure release influenced the t ensile strength. The chemical treatment resulted in lignin sulfonation while carboxylation produced fiber swelling and, consequently, tensil e strength decreased.