The wood industry generally uses synthetic adhesives for bonding wood, although these can be harmful to both humans and the environment. In this thesis we compared well-known urea-formaldehyde adhesive with tannin-based adhesives. We added different additives to the tannin-based adhesives, with the aim of improving the quality of bonding. We used 6 different adhesives and with every adhesive we bonded two three-layered pieces of plywood made from 3 mm thick beech rotary cut veneer. The glue mixture was prepared separately for every type of board, and applied at the amount of 250 g/m2. The bonded plywood was compressed for 15 minutes at a temperature of 150 °C and specific pressure of 18 bars. The bonded plywood was then sawn into test specimens with standard dimensions, and these were tested for bending strength, modulus of elasticity and shear strength. The test specimens that were used to examine the bending strength were also used to examine the density and moisture content of the bonded plywood. Before testing we put all the test specimens in a standard air-conditioned climate, and the half of test specimens for examining the shear strength were additionally immersed in water for 24 hours. The results partially confirmed the hypothesis that tannin-based adhesives can bond veneer plywood to a comparable degree of quality and bending properties to those seen with traditional plywood bonded using urea-formaldehyde adhesives. The plywood bonded with tannin-based adhesive with the addition of sodium hydroxide had the best results with regard to shear strength in comparison to the boards bonded with urea-formaldehyde adhesive.
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