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Optimization of Isocyanate Content in PF/pMDI Adhesive for the Production of High-Performing Particleboards
Due to the fact that impregnation with fire retardant usually reduces the strength of the produced particleboards, this research was carried out to investigate whether it is possible to use phenol–formaldehyde (PF) resin modified using various amounts (0%, 5%, 10%, 15%, and 20%) of polymeric 4,4′-methylene diphenyl diisocyanate (pMDI) for this purpose. The need to optimize the addition of pMDI is particularly important due to health and environmental aspects and high price. Furthermore, the curing process of hybrid resins is still not fully explained, especially in the case of small loadings. Manufactured particleboards differed in the share of impregnated particles (50% and 100%). The mixture of potassium carbonate and urea was used as the impregnating solution. Based on the outcomes of hybrid resins properties, it was found that the addition of pMDI leads to the increase in solid content, pH, and viscosity of the mixtures, to the improvement in resin reactivity determined using differential scanning calorimetry and to the decrease in thermal stability in the cured state evaluated using thermogravimetric analysis. Moreover, particleboard property results have shown that using impregnated particles (both 50% and 100%) decreased the strength of manufactured boards bonded using neat PF resin. However, the introduction of pMDI allowed us to compensate for the negative impact of fire-retardant-treated wood and it was found that the optimal loading of pMDI for the board containing 50% of impregnated particles is 5% and for board made entirely of treated wood it is 10%.
Alternative Wood Raw Material Sources in Particleboard and OSB Production—Challenges and Perspectives
This review examines the potential use of alternative wood raw materials, including fast-growing plantation species, juvenile wood, non-plantation species, and recycled wood, in the production of particleboard (PB) and oriented strand board (OSB). In light of the ongoing challenges faced by the wood-based industry in securing a stable and sustainable supply of raw materials, these alternatives present several advantages, such as cost-effectiveness, greater availability, and reduced reliance on natural forest resources. Fast-growing plantation species and juvenile wood are particularly suited for lightweight applications, while non-plantation species and recycled wood contribute to sustainability goals by lowering environmental impact and promoting resource efficiency. Nonetheless, the successful integration of these materials requires overcoming certain challenges, including variability in their physical and mechanical properties, as well as the need for tailored adhesive systems and processing parameters. This review examines strategies to optimize production processes and enhance the utilization of waste materials while emphasizing the role of alternative raw materials in advancing circular economy principles. The findings highlight the importance of future research to improve material knowledge, technological solutions, and industry practices, thereby supporting the sustainable development of the wood-based materials sector.
Activated Carbon from Coconut Shells as a Modifier of Urea–Formaldehyde Resin in Particleboard Production
Various methods for the effective modification of urea–formaldehyde (UF) adhesives, aimed at enhancing the performance of wood-based materials, have been continually explored worldwide. The aim of this work was to investigate and evaluate the effect of introducing small amounts (0.25–1.5%) of activated carbon from coconut shells (ACCS) in UF adhesive on the properties of particleboard. The performed investigations of the adhesive mixture’s properties showed an increase in both viscosity and reactivity. Moreover, the use of loadings of 0.75% and 1% had a positive effect on mechanical properties such as bending strength, modulus of elasticity, and internal bond. In these variants, a delay in the degradation of the adhesive bonds by water was also observed, as indicated by the lower thickness swelling values measured after 2 h. However, under long-term exposure to water, the modification had no considerable effect on the dimensional stability of the boards. Markedly, the addition of 1 and 1.5% of ACCS resulted in a reduction in formaldehyde content, which can be attributed to the excellent adsorption capacity of activated carbon. Overall, a loading of 1% was found to be optimal, resulting in improved strength, enhanced water resistance, and reduced formaldehyde content.