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Various flours were added as fillers for urea-formaldehyde (UF) resin, and effects on the rheological behavior and the curing properties of the resin were evaluated. The plywood properties such as bonding quality, bending strength, modulus of elasticity, and formaldehyde-release were tested. Five types of flours were used, i.e., rye flour, hemp flour, coconut flour, rice flour, and pumpkin flour. The type of flour had a major influence on the properties of resin mixture such as gel time, solid content, and viscosity. The use of rye and pumpkin flour resulted in a longer gelling time, and the adhesive mixture filled with rice flour did not attain the desired viscosity value needed for the production of plywood. The best mechanical properties and bonding quality were achieved by addition of pumpkin flour. However, the bonding quality of plywood glued with an adhesive filled with every other flour retained good values exceeding 1 N/mm² as required by the standard EN 314-2 (1993). The use of hemp flour as a filler for UF resin led to a substantial decrease of free formaldehyde content. [ABSTRACT FROM AUTHOR]

This study evaluated the possibility of producing oriented strand boards (OSB) from non-strand chips. Properties of the produced boards were compared with commercially available OSB/3. Research has shown that replacing the strand chips of external layers with smaller chips allowed for the manufacturing of OSB/3 using chips up to four times shorter than standard strand chips. Oriented strand board manufacturers should consider preparing a new standard and introducing the market to a new type of OSB with very good mechanical properties and made of selected strand chips comprising one of the fractions obtained during screening. [ABSTRACT FROM AUTHOR]

This study concerns the influence of selected fungi on changes in physical and mechanical properties of type P2 particleboards intended for use in dry conditions. The tested fungi included Aspergillus niger van Tiehgem, Chaetomium globosum Kunze et Fr., Trichoderma viride Persoon ex S.F., Gray aggr., and Penicillium funiculosum Thom. The incubation process lasted for 16 weeks, yet samples for the strength test were selected after a period of four weeks. The degradation level of boards was estimated by measuring the decrement of initial mass and changes in physicomechanical properties. The obtained results showed that mechanical strength of the investigated boards affected by the tested fungi decreased by 15% to 20%. However, the differences in DSC thermographs indicate that it is cellulose that mainly undergoes degradation in the wood of the investigated boards. Based on the changes in mechanical properties and DSC analyses, we consider T. viride and A. niger as the most aggressive fungal species. [ABSTRACT FROM AUTHOR]

Strand substitution was evaluated for the core of OSB with chips produced by grinding of recycled particleboards and wood waste. All the boards manufactured under laboratory conditions having a share of small chips in the core had high mechanical parameters, thus meeting the requirements of the standard for OSB/3. No significant effect was found of the applied modification of the core on bending strength or modulus of elasticity (MOE) determined for the longer axis. In turn, such properties as modulus of rupture (MOR) and MOE, determined for the shorter axis, as well as internal bond (IB) were rapidly reduced. In the case of boards containing 100% recycled chips in the core, a reduction was found in values of MOR, MOE, and IB by 45%, 30%, and 45%, respectively. In turn, the application of small chips, which previously had not been resinated, makes it possible to manufacture boards with internal bond lower by only 30%, even at the 100% substitution. Application of recycled chips produced by grinding of the P2 type particleboard did not make it possible to manufacture boards meeting the requirements of the standard after the boiling test, irrespective of the amount of small chips added to the core. Boards containing in their core small chips, which previously had not been resinated, had much better properties in this respect, since only in case of 100% substitution the manufactured boards exhibited internal bond after the boiling test lower than the requirements of the standard EN 300. [ABSTRACT FROM AUTHOR]

Physical and mechanical properties were evaluated for industrial and laboratory boards intended to be used in the construction industry. The boards were subjected to accelerated aging tests including resistance to humidity in the conditions of cyclic test in accordance with EN 321 (2002), and determination of dimensional changes resulting from changes in relative humidity according to EN 318 (2002). The greatest changes were observed after one test cycle. Moreover, the boards made of fine chips demonstrated slightly higher resistance to the tested factors. Although laboratory boards showed a much lower density, their behavior following the exposure to the assessed factors was similar to that of industrial plates. [ABSTRACT FROM AUTHOR]

The influence of selected technological aspects was studied relative to characteristics of oriented strand lumber (OSL) boards manufactured from pine strands. Six types of boards were prepared, differing in the strand fraction size, density (700 kg/m3 and 800 kg/m3), and adhesive used to glue the strands in the core layer. The adhesives compared were melamine-urea-formaldehyde (MUF) and polymeric diphenylmethane diisocyanate (pMDI). The results showed that the OSL boards had good physical and mechanical properties, even though pine strands of diverse characteristics, particularly in terms of their length and width, were used for their production. The influence of strand size was clear in the results of the bending and elongation tests. Both for the bending test and tensile strength in a direction parallel to the wood grain, the properties were on average 20% greater for boards made of larger strands compared to those made of smaller strands. However, the latter demonstrated greater internal bonding strength (IB). The weakness of OSL boards made from small strands was their low modulus of elasticity, particularly when the board density was simultaneously reduced. [ABSTRACT FROM AUTHOR]

This paper investigated the possibility of using very fine wood chips for the production of P5 type building boards according to the EN 312 (2010) standard. Small wood chips are more evenly compressed during mat pressing because they have a high bulk density. Therefore, the beneficial effects of forming denser outer layers is lost. To achieve the desired shape of the density profile curve of a board, the moisture content of the chips used in the outer face layers was increased considerably (up to about 30%). As a result of the conducted tests, the mechanical properties of the manufactured boards met the EN 312 requirements for P5 boards above a density of 650 kg/m³. In cases when the additional conditions are being met, the standard requirements may be met at an even lower density level of approximately 550 kg/m³. [ABSTRACT FROM AUTHOR]

This paper describes an attempt to use long fibres from fast growing hemp (Cannabis sativa L.) as a raw material for the production of boards for the building and furniture industry. Hemp fibre boards with densities of 300 to 1100 kg/m3 were studied. The board surfaces were finished using a one-cycle method in which birch veneers were pressed to make the boards. The pulp was glued with pMDI (9 wt.% based on dry weight). The basic mechanical and hydrophobic properties of the boards were tested. The static bending strength and modulus of elasticity of the boards with a density of about 650 kg/m3 were comparable to P2 furniture boards. Only the higher density boards had adequate properties that met standards for the building industry, which were comparable to those of OSB/3 and MFP boards. Hemp fibre boards were characterised by relatively good water resistance, which was manifested by low swelling and low soaking susceptibility. [ABSTRACT FROM AUTHOR]