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The aim of the presented study was to apply various bark species (birch, beech, maple, pine and spruce) as fillers for urea-formaldehyde (UF) resin in three-layer plywood manufacturing. For this purpose, all types of bark were ground and added to the adhesive mixture. The resultant plywood was subjected to investigations of the following: tensile strength, modulus of elasticity (MOE), bending strength (MOR) and formaldehyde emission. The results indicate a reduction in the tensile strength. Moreover, the lack of significant improvement in strength parameters can be explained by too high a load of the filler (20 wt%). In the case of formaldehyde emissions, a reduction was observed for birch (B-1), beech (B-2), maple (B-3) and pine bark (B-4). In addition, an increase in the emission of formaldehyde was recorded only for spruce bark. [ABSTRACT FROM AUTHOR]

The possibility of replacing the rye flour commonly used as a filler for urea formaldehyde resins was investigated for plywood production with birch bark characterized by various particle dimensions. The effects on the curing and rheological properties of the adhesives were investigated. Moreover, the plywood was tested to evaluate the formaldehyde emissions, bonding quality, modulus of elasticity, and bending strength. The results showed that the size of the bark particles had a significant effect on the viscosity of the adhesives but did not affect other properties of the resin. Replacing the flour with the bark significantly decreased the formaldehyde release, but there was no clear correlation with the dimensional fraction of the bark powder. The particle size had notable effects on bonding quality and mechanical properties. The best results were obtained for a sieve with square holes whose inside lengths were 0.315; however, all plywood samples achieved shear strength values exceeding the requirements of EN 314-2 (1993). [ABSTRACT FROM AUTHOR]

This research evaluated the possibility of using sawmill by-products from the roundwood-processing line in the production of wood-based panels. Due to its number of favorable properties, interesting chemical composition and large reserves resulting from the lack of industrial applications, the research focused particularly on the use of bark. Manufactured variants of boards differed in the proportions of wood chips to bark (70:30, 60:40, 50:50). Moreover, the boards containing only wood chips and a mixture of chips and sawdust were used as references. Urea-formaldehyde adhesive mixed with ammonium nitrate as a hardener was applied as a binding agent for the boards. Based on the mechanical properties (modulus of elasticity, modulus of rupture, internal bonding), physical properties (density, thickness swelling, water absorption) and content and emission of formaldehyde, it was found that it is possible to produce boards characterized by good properties from sawmill by-products without advanced processing. Moreover, the use of bark instead of sawdust in order to increase the homogeneity of the cross-section allows one to obtain panels with significantly lower formaldehyde emission and water uptake. [ABSTRACT FROM AUTHOR]