form strong cross link in the final boards [44,45] and thus subsequently forms stronger boards. In contrast, the TS decreased with increased board density(Table 5). Compared to high density boards, low density boards have more spaces and voids. This caused the water to penetrate into the boards more easily. Therefore, the density of the boards influences the TS of the boards. As a result, the optimum board density was 250 kg/m3.