The properties of particleboards and the course of their manufacturing process depend on the characteristics of wood particles, their degree of fineness, geometry, and moisture content. This research work aims to investigate the physical properties of wood particles used in the particleboard production in dependence on their moisture content. Two types of particles currently used in the production of three-layer particleboards, i.e., microparticles (MP) for the outer layers of particleboards and particles for the core layers (PCL), were used in the study. The particles with a moisture content of 0.55%, 3.5%, 7%, 10%, 15%, and 20% were tested for their poured bulk density (ρp), tapped bulk density (ρt), compression ratio (k), angle of repose (αR), and slippery angle of repose (αs). It was found that irrespective of the fineness of the particles, an increase in their moisture content caused an increase in the angle of repose and slippery angle of repose and an increase in poured and tapped bulk density, while for PCL, the biggest changes in bulk density occurred in the range up to 15% of moisture content, and for MP in the range above 7% of moisture content, respectively. An increase in the moisture content of PCL in the range studied results in a significant increase in the compression ratio from 47.1% to 66.7%. The compression ratio of MP increases only up to 15% of their moisture content—a change of value from 47.1% to 58.7%.

The aim of presented work was to investigate whether it is possible to use ground pine needles as a formaldehyde-scavenging filler for urea-formaldehyde resin in the production of plywood. The scope of the research included determinations of both optimal amount of introduced filler and the effect of its modification (silanization, hydrothermal and alkaline treatments). Properties of adhesives such as viscosity, gel time and pH were investigated and their morphology was assessed using scanning electron microscopy. Manufactured plywood were tested in terms of wet shear strength, tendency to delamination and formaldehyde emission. It was found that the addition of pine needles lowers the pH and reduces gel time of the adhesive. Moreover, it was shown that despite a significant reduction in formaldehyde emission, the addition of non-modified needles causes a decrease in bonding quality of plywood. Based on the results, 10 parts by weight of needles per 100 parts by weight of resin can be considered as optimal loading. The use of ground needles modified hydrothermally and with silane allows to minimize the negative effect on the strength of glue lines and leads to further reduction of formaldehyde emission. Therefore, it can be concluded that pine needles powder has a strong potential for the application as formaldehyde-scavenging filler for urea-formaldehyde adhesive in plywood production.