Optimization of Isocyanate Content in PF/pMDI Adhesive for the Production of High-Performing Particleboards

Abstract

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%.

Preparation and Characterization of Particleboard Made from Industrial-Type Wood Particles and Discarded Duck Feathers

“…The highest WA was found in panel 6 after 2 h and 24 h. It is worth noting that panels 3 and 4, bonded with pMDI, had the best physical properties, showing no significant differences in physical properties between those with and without feathers and with less swelling equilibration between 2 h and 24 h compared to those of the panels produced with UF and PVAc adhesives. This superior performance of pMDI-bonded panels can be attributed to the extensive crosslinking reactions between the isocyanate groups of the resin and the hydroxyl groups present in wood, as well as the amines in feathers during curing [51,52], resulting in a highly crosslinked polymer network that enhances water resistance and reduces swelling. Conversely, UF and PVAc resins may exhibit lower resistance to moisture due to their less robust crosslinking and polar nature compared to pMDI [53][54][55], resulting in inferior physical properties.…”

Properties of sandwich boards with a core made of bio-composite particleboard containing wood particles and walnut shells

“…It has the ability to create covalent bonds with the surface functional groups of lignocellulosic raw materials. The moisture contained in them accelerates their curing (Kawalerczyk et al 2023). Walnut shells are rich in cellulose, hemicelluloses, lignin, and pectin, which provide a signi cant number of hydroxyl groups available for bonding (Pirayesh et al 2012; Dobrzyńska-Mizera et al 2019).…”