Three-layered composite materials consisting in wood-chips bonded by a resin (particleboard) were successfully produced from two by-products: plum and apple tree branches, waste biomass produced after orchard pruning; a third particleboard was made from an industrial softwood blend as a reference. After collecting the branches, the raw materials were characterized in matters of density, bark content and bulk density of particles. Various physical and mechanical properties were assessed in accordance with European Standards for wood-based panels, namely thickness swelling, water absorption, modulus of rupture, modulus of elasticity, internal bonding strength, screw withdrawal resistance, as well as density profile and machining properties during milling and drilling. Modulus of rupture was 14.4 ± 1.2 N mm −2 for plum-based panels and 12.8 ± 2.3 N mm −2 for apple-based panels, while modulus of elasticity was 2576 ± 140 N mm −2 for plum-based panels and 2432 ± 345 N mm −2 , which fulfills the mechanical requirements for panels of furniture production and interior equipment purposes which of this kind of materials is modulus of rupture of 11 N mm −2 and modulus of elasticity of 1600 N mm −2. The results showed in general, a good performance of the composite materials elaborated from waste biomass, thus offering a potential revalorization of a rather undervalued by-product.

The sizeable global production of wood-based products requires new sources of raw material, but also creates large quantities of wastes or composites that do not comply with requirements. In this study, the influence of different shares of recovered high-density fiberboards (HDF-r), reversed into the production, on industrial HDF properties, has been examined. HDF-r may be a suitable partial substitute for raw pinewood for industrial HDF production. Although most of the mechanical properties, as well as thickness swelling and water absorption, had a linear decrease with the increase in the share of HDF-r share, the elaborated boards met most of the commercial requirements (EN 622-5). The property that did not meet the requirements was the internal bond strength for panels with 10% of HDF-r. The presented results show that, after some adjustments, it should be possible to produce HDF boards with up to 10% of recycled HDF being able to meet all commercial requirements.

The growing production of wood-based panels and the linked consumption result in a need for substituting standard wooden raw materials. The shortage of wood availability, as well as the increasing prices and a trend towards more environmentally friendly materials and processes, have encouraged the producers of wood-based products to consider extending the life cycle of wood composites. In the present work, the influence of substituting pine with spruce for industrial high-density fiberboards with 5% of recovered fibers was studied. Samples containing 0%, 25%, 50%, and 100% spruce fibers were tested in their mechanical resistance and their interaction with water. Boards from all samples met relevant standard requirements; however, the addition of spruce caused a decrease in mechanical properties, with homogeneity having the most significant influence. The modulus of rupture dropped up to 6% and the internal bond for 47% for samples having 50% of spruce. The most significant drop (50%) was observed for surface soundness for samples made with 100% spruce. Regarding physical properties, swelling increased up to 19% with 50% spruce; on the other hand, its water absorption decreased for up to 12%. The addition of spruce to industrial high-density fiberboards also influenced the formaldehyde content negatively, with an increase of up to 21% with 50% spruce. Graphic Abstract

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Wood quality depends on many circumstances, as it is sensitive to changing properties, depending on the environment. This work evaluates the influence of moisture content of selected wood-based composites on their basic mechanical properties, i.e., modulus of rupture and modulus of elasticity. The selected panels were divided by application in construction materials and furniture materials, which demand specific conditions during service-life. The increase of moisture content in different types of wood-based panels resulted in a slight reduction of the modulus of rupture and the modulus of elasticity. Boards for use in dry conditions, mainly in the furniture industry, were more sensitive to lowering their modulus of elasticity with higher board moisture content compared with those designed for humid conditions, mainly from the building industry.