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Subsequently, a 5-min cold pre-press was carried out inside the mold box. The flakes were arranged inside the press between two aluminum layers, separated by two 12 mm thick steel bars to ensure the target board thickness. The flakes were pressed using a hydraulic press. For the boards, a pressing factor of 1.6 min/mm was applied, and a temperature of 180 ◦ C was used for all three types of adhesives. A maximum pressure of 35 bar was applied at the beginning. After 70% of the cycle time, the pressure was reduced to 15 bar, and after 85% of the time, it was further reduced to 5 bar, as shown in Figure 1. This gradual reduction was intended to prevent sudden steam release and thus avoid board delamination. The OSB panels were stored at room temperature for 7 days immediately after pressing.
Figure1. Pressing cycle for the manufacture of OSB panels.
Three different OSB panels were manufactured: a control sample (OSB-C) using phenol-formaldehyde adhesive, and two samples (OSB-1 and OSB-2) employing green adhesives. Five replicates of each OSB sample, with dimensions of 40 cm in length × 40 cm inwidth × 1.2 cm in thickness, were produced using 90 g of adhesive and an open time of 2 min. Additionally, it is important to note that there was no difference in the manufacturing process among the samples. Finally, a squaring saw was used to cut the OSB panels for the determination of their physical, mechanical, and thermal properties, as well as formaldehyde emissions, following the respective specifications of the European and American standards. 2.3. Assessment of Accelerated UV Weathering Accelerated UV weathering was assessed following the ASTM G154 [23] standard specifications, using three specimens per OSB sample with dimensions of 290 mm in length × 50 mm in width, which were exposed to a continuous UV weathering cycle. A general factorial experimental design was conducted using Design Expert ® V10.01 software to examine the impact of color change and surface appearance of the tested OSB panels based on the adhesives used. These adhesives were the factors considered, and the response variable was the CIELAB color change. 2.4. Physical Properties Density was measured following the UNE-EN 323 [24] standard specifications on six specimens per OSB sample with dimensions of 50 mm in length × 50 mm in width. Moisture content was measured following the UNE-EN 322 [25] standard specifications on four specimens per OSB sample with dimensions of 50 mm in length × 50 mm in
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