The depletion of natural resources and increased demand for wood and wood-based materials have directed researchers and the industry towards alternative raw materials for composite manufacturing, such as agricultural waste and wood residues as substitutes of traditional wood. The potential of reusing walnut (Juglans regia L.) wood residues as an alternative raw material in particleboard manufacturing is investigated in this work. Three-layer particleboard was manufactured in the laboratory with a thickness of 16 mm, target density of 650 kg∙m⁻³ and three different levels (0%, 25% and 50%) of walnut wood particles, bonded with urea-formaldehyde (UF) resin. The physical properties (thickness swelling after 24 h) and mechanical properties (bending strength, modulus of elasticity and internal bond strength) were evaluated in accordance with the European standards. The effect of UF resin content and nominal applied pressure on the properties of the particleboard was also investigated. Markedly, the laboratory panels, manufactured with 50% walnut wood residues, exhibited flexural properties and internal bond strength, fulfilling the European standard requirements to particleboards used in load-bearing applications. However, none of the boards met the technical standard requirements for thickness swelling (24 h). Conclusively, walnut wood residues as a waste or by-product of the wood-processing industry can be efficiently utilized in the production of particleboard in terms of enhancing its mechanical properties.

In this study, wood plastic composites (WPC) made of poly(lactic acid) PLA and a bark-filler were manufactured. Two degrees of bark comminution (10–35 mesh and over 35 mesh) and varied content of bark (40, 50 and 60%) were investigated. The studied panels were compared with analogically manufactured HDPE boards. The manufacture of composites involved two stages: at first, WPC granules with the appropriate formulation were produced using the extruder (temperatures in individual extruder sections were 170–180 °C) and crushing using a hammer mill after cooling the extruded composite; secondly, the obtained granulate was used to produce boards with nominal dimensions of 300 × 300 × 2.5 mm3 by flat pressing in a mold, using a single daylight press at a temperature 200 °C. The study proved that comminuted bark can be applied as a filler in PLA composites. However, an increase in bark content decreased mechanical properties (MOR, MOE) and deteriorated humidity resistance (high TS and WA) of the panels. Along with the increase in bark content, an increase in the contact angle of the composite surfaces and a decrease in the total surface energy were noted. It was also found that PLA composites have higher strength parameters and lower moisture resistance compared to HDPE composites with the same bark content.Graphical abstract

Increased demand for wood affects its price and thus contributes to the growing interest in raw materials that can be used as a partial or total substitute for wood in the production of particleboard. One of the raw materials for the production of particleboard can be Cannabis sativa or, more precisely, hemp shives. In this work, 7 variants of panels with a density of 650 kg/m³ with 10 and 25% hemp shives substitution in different layers were produced. Particleboards containing hemp shives were characterized by lower density compared to conventional particleboards. The shares of hemp shives at the levels of 10% and 25% have a slight impact on the MOR and MOE; additional IB showed no statistically significant differences between the conventional particleboards and particleboards with a share of hemp shives. For particleboards with 25% hemp shives, a reduction in swelling was observed relative to particleboards made entirely of industrial wood particles.

The study aimed to determine the suitability of agricultural lignocellulosic biomass in the form of vine pruning waste for particleboard production. Two variants of particleboards with densities of 650 kg/m³ and 550 kg/m³ containing a varied amount of vine pruning waste (0, 25, 50 and 100%) were evaluated. The strength (MOR, MOE and IB), thickness swelling and water absorption after immersion in water for 2 and 24 h were tested. The results revealed that vine pruning waste affected the board thickening and reduced strength properties. Boards with a 50% share of waste met the minimum requirements of strength properties specified in the EN 312 standard for boards with a density of 650 kg/m³. However, boards with a density of 550 kg/m³ entirely made with vine pruning waste met the minimum requirements of strength properties of the EN 16368 standard. Moreover, the pruned material reduced axial forces during drilling, swelling and water absorption.

1,3-dimethyl-4,5-dihydroxyethyleneurea (DDHEU) and 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) were used as the binders in 3-mm high density fiberboard (HDF) manufacturing. The studies focus on the physical and mechanical properties of boards bonded with DDHEU or DMDHEU as a potential substitute for typically used urea-formaldehyde (UF) resins. The adhesive loads were 8% or 12%. The UF-bonded boards of same resin load were used as the controls. Applied pressing time ranged between 4 and 5 minutes. The results indicate that the use of DDHEU or DMDHEU as binders enhanced physical and mechanical properties of the boards. It was found that properly set pressing scheme and resin type allowed produce DDHEU- and DMDHEU-bonded HDF that exhibited comparable or superior performance when compared to the UF-bonded reference series and complied with European Standards. The best performing boards exhibited internal bond 1.3 MPa, modulus of elasticity 9656 MPa, modulus of rupture 56.5 MPa, thickness swelling 14% and formaldehyde release below 3.0 mg/m²h. Due to low reactivity of DDHEU and DMDHEU at temperatures below 160°C, the approach is effective for thin boards only.