# Physico-Mechanical Properties of Particleboards Produced from Macadamia Nutshell and Gum Arabic
## 3 Results
### Mechanical Properties  
The one-way ANOVA analysis shown in Table 5 indicated that the modulus of rupture and modulus of elasticity presented a significant difference between the four treatments at a significance level of 5% (F\({}_{3.16}\) = 439.60; \(p\) < 0.05 and F\({}_{3.16}\) = 58.23; \(p\) < 0.05). Treatment T4 \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Treatment** & **Density (kg/m\({}^{3}\))** & **MC (\%)** & **WA (2 h) (\%)** & **TS at 2 h (\%)** & **WA at 24 h (\%)** & **TS at 24 h (\%)** \\ \hline T1 & 818.60 1  & 6.90 & 25.95 & 6.06 & 38.76 & 28.46 \\  & (15.59) 1  & (1.05) & (1.64) & (0.58) & (3.32) & (0.81) \\ T2 & 106.733 & 12.18 & 12.87 & 3.33 & 24.17 & 21.67 \\  & (4.41) & (0.66) & (0.25) & (0.58) & (0.13) & (0.71) \\  & 1128.53 & 12.18 & 12.87 & 1.50 & 14.48 & 17.39 \\ T3 & (10.29) & (0.05) & (0.73) & (0.50) & (0.42) & (1.21) \\  & 1219.20 & 13.45 & 8.12 & 0.00 & 9.42 & 6.22 \\ T4 & (25.56) & (0.12) & (0.97) & (0.00) & (0.28) & (3.30) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Physical properties. had the highest value of modulus of rupture and modulus elasticity which was 12.21 MPa and 1.81 GPa, respectively, while the lowest value was 4.32 MPa and 1.05 GPa for treatment T1. The relatively high values of modulus of rupture and modulus of elasticity recorded for treatment T4 could be due to the random distribution of the particles in the composites. [PERSON] et al. [26] reported a similar conclusion by mixing wood residues with cement to fabricate particleboard. On the other hand, the modulus of rupture and the modulus of elasticity increased with the increase in the density of the boards, and this was due to the high specific gravity of the two materials. It was also observed that the panels did not have a good resistance in flexion, and this was due to the natural shape of the macadamia nutshell particles; adding fiber reinforcement could increase the strength. The American National Standard Institute specifies the minimum modulus of rupture and modulus of elasticity are 3.00 N/mm\({}^{2}\) and 550 N/mm\({}^{2}\), respectively, while the maximum is 23.5 N/mm\({}^{2}\) and 3100 N/mm\({}^{2}\), respectively, for general-purpose particleboards. According to the findings of this research, the boards produced using an adhesive-macadamia nutshell ratio of the four treatments met the requirements specified by the ANSI/A208.1-1999 for general-use particleboards, and only the mixing ratio of T4 met the minimum required for grade M-1. The test results showed that the compressive strength varied in the range between 8.88 MPa for treatment T1 and 22.54 MPa for treatment T4. The one-way ANOVA analysis reported that there was a significant level of difference between the four treatments (F\({}_{3,8}\) = 148.62; \(p\) < 0.05). The increasing compressive strength could be due to the decreasing number of voids in treatments T3 and T4 as shown in the scanning electron microscopy images and the compaction between the macadamia nutshell particles and the gum Arabic adhesive, thereby achieving good chip-to-chip contact during the pre-compression phase. The compressive strength results were not surprising since the two materials showed desirable specific gravity and bulk density. The density of the panel increased with the increase in the compressive strength. Moreover, macadamia nutshell is known to be tough and has good resistance in compression [13]. The tensile strength value ranged between 1 N/mm\({}^{2}\) for treatment T1 and 1.25 N/mm\({}^{2}\) for treatment T4. The one-way ANOVA analysis showed that there was a significant level of difference for the four treatments. The tensile strength also increased with the increasing in gum Arabic adhesive in the mixing design. The high tensile strength in treatment T4 could be due to the good adhesion between the two materials, which reduced the number of voids compared to treatment T1 and T2.