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The internal bond strength (IB) results of the different samples were in the range of 0.62 MPa (OSB-2) to 0.95 MPa (OSB-C), where the OSB-1 and OSB-2 samples reached 85.23% and 65.26%, respectively, of the IB strength measured in the control sample OSB-C. Additionally, the OSB-1 sample showed no significant statistical differences compared to the control sample OSB-C, while the OSB-2 sample did present significant statistical differences compared to the OSB-C sample. These results are consistent with and higher than those obtained by various authors who manufactured OSB panels using PF modified with canola protein and ammonium adhesives [19], or partial substitution of pMDI with lignin-containing cellulose nanofibrils [16], among others. In both cases, tensile strength and internal bond strength, there were no statistically significant differences between the OSB-C and OSB-1 samples, indicating that the OSB panels manufactured with GA1 exhibited the same performance as panels manufactured with phenol-formaldehyde adhesive. This also indicates good adhesion, efficient resin spreading, and fine atomization [39]. These properties reflect the weakest layer within the panel [40]. These findings underscore the significance of optimizing panel structure, resin type, and fabrication parameters to enhance internal bond and overall panel quality [41]. The Janka hardness results of the different samples ranged from 7669 N (OSB-2) to 8896 N (OSB-C), with OSB-1 and OSB-2 reaching 87.47% and 86.21%, respectively, of the hardness obtained by the control sample OSB-C. In severe end-use surfaces, hardness plays an important role [42]; for example, it is a property that can significantly affect repeated use [43]. In this case, where there were no significant statistical differences between all three samples, the OSB panels produced with green adhesives had statistically the same performance as the OSB panel manufactured with a formaldehyde-based adhesive. Furthermore, the increase in hardness is related to OSB density [42], which could explain the similar results, given that the OSB panel densities were similar. In general, based on the results obtained for bending properties and internal bond strength, all three types of OSB panels tested could be classified as structural panels for use in dry environments, corresponding to technical class OSB/2, according to the UNE-EN 300 [44] standard. Nevertheless, the thickness swelling results do not meet the requirement. However, it is important to note that the OSB-GA panels do not include the incorporation of kerosene or any hydrophobic product, which was included in the control OSB sample. This means that the OSB panels manufactured with GA exhibited similar behavior and quality to OSB panels manufactured with phenol-formaldehyde adhesive, considering the aforementioned properties. After analyzing the performance of the OSB-C, OSB-1, and OSB-2 samples under mechanical testing, it is important to mention the difference in the results observed in the OSB-2 sample compared to the OSB-C and OSB-1 samples. This difference could be associated with the characterization and composition of the wood adhesives used, or with differences in the OSB density results, which ideally should have been similar, considering that the manufacturing process and conditions were the same. This difference in densities could explain why the mechanical properties of the OSB-2 sample did not fall within the range of the other samples. This may be due to the elastic recovery of wood, known as “spring-back” [45], where the OSB panels manufactured with green adhesives exhibited increased thickness after pressing, resulting in a larger volume and therefore lower density, and ultimately, a higher degree of spring-back.
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