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The empty spaces in the microstructure of a system are classified by the International Union of Pure and Applied Chemistry (IUPAC) as micropores, mesopores, and macropores (Santos et al. 2014), as shown in Table 3. Table 3. Pore Classification Classification Pore size Micropores diameter < 0.002 μm Mesopores 0.002 μm<diameter < 0.05 μm Macropores diameter > 0.05 μm According to Table 3, all OSB types present macropores. The presence of macropores in each type of OSB is related to anatomical aspects of the wood. Because of the stochastic manner in which OSB is formed, as well as the differences in sizes of the strands, one can expect there to be a high frequency of empty spaces within the structure. The amount of resin applied, in combination with the applied pressure, is not likely to be large enough, during practical manufacturing conditions, to fill eliminate such pores between the strand elements. All panels in this study were pressed with 4.0 MPa. Nonetheless, Bertolini et al. (2019) analyzed the porosity for Pinus sp. particleboards pressed with 4.5 and 2.5 MPa. Porosity of panels were influenced by intensity of pressure during their manufacturing, being large for panel of 2.5 MPa. The use of uniform particles in the production of panels enables the occurrence of a larger voids, as these ordinarily would be filled with smaller particles. Schizolobium amazonicum , used in the production of OSB 1 and 2, is a low-density wood (390 kg/m³). It shows no difference between heartwood and sapwood, and lacks knots. The low density contributes for more workability of the species, and these factors collaborate to generate particles with more uniform dimensions. Pinus sp. and the Corymbia citriodora (with a density of 490 kg/m³ and 700 kg/m³, respectively), show differences between the heartwood, sapwood, and knots, thus making particles with less uniformity. The utilization of smaller particles in the manufacture of the panels reduces the empty spaces; thus, the number of pores in the panel decreases. Allied to this are the pore diameters related to each species of wood, as already commented. It is also noteworthy that in addition to the reduced pore diameter compared to the other species under study, Corymbia citriodora has pores filled with tyloses. Expansion of the cell wall of a parenchyma cell adjacent to a vessel element, through the opening of a puncture, partially or completely blocking the lumen diameter. Tyloses in wood cause effects such as vessel closure causing low wood permeability. The obtained results were compared to the literature. Varanda (2016), for example, analyzed the porosity of particleboard produced with Pinus sp. and peanut shell, glued with oil-based polyurethane resin beaver. Results showed a porosity of 33.7%, a value very similar to obtained in this study for treatments OSB 1 and OSB 4 (both produced with Pinus sp.). Bertolini et al. (2019) obtained approximate value of 54% for particleboard produced with Pinus sp. waste materials, which were treated with copper chrome boric oxide preservative and glued with castor oil-based polyurethane resin. This result is similar to that obtained for OSB 2 and OSB 3. This result is very important for wood construction industry, especially in Brazil, where most of the houses are manufactured with OSB. Characteristics such as thermal conductibility and acoustic comfort are very important, and are used improved with the addition of other material as glass wool, pet wool. The porosity of the panel can improve
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Ferro et al . (20 21). “Strandboard Hg porosimetry,” B io R esources 16(4), 6661-6668.
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