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journal of materials research and technology 2022;20:4630 e 4658
Fig. 15 e Modulus of rupture (MOR) e density chart for particleboard (400 e 650 kg/m 3 ) made with agricultural biomass and conventional wood.
Andrade et al. [170] studied particleboard ' s physical and mechanical properties from different proportions of ther- mally treated recycled pine particles. The authors also per- formed a chemical composition analysis for the thermal- treated recycled particles. TS and WA values of particleboard made from thermally treated particles were not significantly lower than those of the control panels. However, conferences produced with particles treated at 220 C showed a significant reduction in WA compared to other samples. This result was in agreement with those obtained by Paul et al. [171]. This phenomenon was explained by the partial degradation of hemicelluloses, which was reflected in the thermogravimetric analysis results. The relative content of lignin and cellulose showed an increment. The IB decreased slightly but complied with the specification (0.10 N/mm 2 ) given in the ANSI standard A208.1/99 for low-density boards. The movement of extrac- tives caused IB reduction in the surface of the particles, which would hinder wood-adhesive bonding [172]. Generally, increasing the proportion of heat-treated particles resulted in a decrease in the MOR and MOE values of the boards. However, the reduction is insignificant. The MOR and MOE decreased with increasing treatment temperature, which was expected as high temperatures degrade the structure of the wood, thus resulting in lower mechanical properties [173 e 176]. The adhesive system used in the production of particle- board also exerts significant influences on the properties of the boards produced. Formaldehyde-based adhesives are some of the most widely used binders in particleboard pro- duction. However, other suitable binders are also being explored but are often used together with formaldehyde-
based adhesive. Li et al. [52] conducted a study investigating the properties of particleboard made from recycled wood bonded with pMDI and PF adhesive with different pMDI to PF ratios. Janiszewska et al. [177] incorporated different liquefied wood waste binders into a conventional UF adhesive system to produce recycled-wood particleboard. For the particleboard produced with different pMDI to PF ratios, the authors found that MOR and MOE values increased with an increasing pMDI to PF ratio. Furthermore, the parti- cleboard produced with higher pMDI contents also showed higher IB. This result was in contrast with that reported by Papadopoulos [182]. However, a combination of other pa- rameters such as mat moisture content, pressing tempera- ture, pressing time, and adding other additives could cause a slight IB difference. The increase in IB was explained by Bao et al. [183] that pMDI could penetrate wood cells and the in- termediate lamellae between them, where it can interact with the accessible moisture held in the wood. Moreover, pMDI may react with the chemical components of the wood (the hydroxyl groups in polysaccharides or the phenolic groups in lignin) to form urethane structures, which are likely to further aid adhesion. Markedly, the TS values reduced when the pMDI to PF ratio increased. Janiszewska et al. [177] investigated the physical and me- chanical performance impact of several types of liquefied wood waste binders and recycled wood particleboard. From the results obtained from the experiment, the authors observed that the MOR and MOE values of recycled-wood particleboard bonded with liquefied wood waste and UF ad- hesive were similar to those of the control particleboard,
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