Effects of Different Adhesive Ratios on Selected Panel Properties of High-Density Fiberboard (HDF) Produced from Fir and Beech Chips

High-density fiberboard (HDF) has been utilized in various forest-based industries for centuries. This study investigated the effects of different adhesive ratios on the properties of HDF through a series of tests. The panels, designed in particular for this study, had been produced in a laboratory putting the usage of a combination of 70% fir (Abies nordmanniana subsp. bornmulleriana) and 30% beech (Fagus orientalis L.) fibers sourced from the western Black Sea area of Turkey. Two adhesive levels were tested: 10.73% for panel I and 11.30% for panel II, both calculated based on dry fiber weight. We assessed several physical and mechanical properties, including density, modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding (IB), hardness, water absorption, and through-thickness swell, in accordance with standard testing methods. The results indicated that both adhesive levels produced panels meeting the general performance requirements for HDF. Panel II, which contained slightly more adhesive, demonstrated marginally better performance in specific strength and dimensional stability tests. Overall, the findings suggest that optimizing adhesive usage in industrial HDF production can help establish a balance between the performance requirements of the boards and cost-effectiveness in production.