Windows, as part of each building, can be wooden, PVC or made of aluminium. Wooden windows look more natural, but they are not durable and resistant enough. Therefore, new windows, made of thermally treated spruce, have appeared in the market. They assure better resistance, compared to the windows made of larch or oak, for lower price. Thermal treatment of spruce is made in an inert atmosphere at the temperatures up to 240 °C. The treated wood becomes more durable, the equilibrium moisture decreases, but some properties deteriorate, for example, the fragility increases, the bending strength decreases, bonding and surface finish are more difficult. In the graduation thesis we measured the bending strength of 3-ply laminated wood for windows as well as the joints shear strengt. We used three different adhesives (Rakoll GXL 4 Plus, Mekol D3 and Purbond HB 440) to bond the lamellas in four different laminates: The first laminate part was made of three thermally not treated spruce lamellas, the second one of three thermally treated lamellas, the third of two external thermally treated and the internal not thermally treated lamella and the fourth with the one external thermally treated lamella and the two lamellas not treated. The highest bending strength had the laminated wood from non treated wood, bonded with Purbond adhesive. Two other adhesives also showed good results, but with a smlaller strength. Based on the results, we suggest bonding of thermally modified wood by one of PVAc adhesives as their price is lower and the quality of bonding is still good enough.
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