## 3 Results
### Mechanical and Morphology Analysis of the Curaua/Composites
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Samples** & **Tensile Strength (MPa)** & **Young’s Modulus (GPa)** & **Flexural Strength** & **Flexural Modulus (MPa)** & **(GPa)** \\ \hline PLA composites & & & & \\ Matrix & a 58.2 \(\pm\) 2.1 & a 5.6 \(\pm\) 0.2 & c 93.5 \(\pm\) 2.4 & a 3.0 \(\pm\) 0.08 \\ CF 10 wt\% & a 57.7 \(\pm\) 1.0 & a,b 5.8 \(\pm\) 0.6 & b,c 91.3 \(\pm\) 1.4 & b 3.6 \(\pm\) 0.1 * \\ CF 20 wt\% & a,b 60.2 \(\pm\) 3.0 & cd 7.3 \(\pm\) 0.5 * & a 82.8 \(\pm\) 3.3 * & c 4.7 \(\pm\) 0.2 * \\ CWM 10 wt\% & b 66.7 \(\pm\) 1.6 * & b,c 6.7 \(\pm\) 0.4 * & c 93.1 \(\pm\) 4.2 & b 3.6 \(\pm\) 0.1 * \\ CWM 20 wt\% & c 75.7 \(\pm\) 4.7 * & e 8.8 \(\pm\) 0.8 * & d 103.6 \(\pm\) 2.0 * & d 4.5 \(\pm\) 0.1 * \\ CHM 10 wt\% & a 57.6 \(\pm\) 1.8 & a,b,c 6.6 \(\pm\) 0.4 * & a,b 87.3 \(\pm\) 1.9 * & b 3.6 \(\pm\) 0.0 * \\ CHM 20 wt\% & a,b 63.4 \(\pm\) 2.2 & d,e 7.9 \(\pm\) 0.4 * & c 92.8 \(\pm\) 2.0 & d 4.4 \(\pm\) 0.1 * \\ PHB composites & & & & \\ Matrix & a,b 18.5 \(\pm\) 1.0 & a 2.5 \(\pm\) 0.09 & a,b 26.3 \(\pm\) 1.0 & a 1.3 \(\pm\) 0.06 \\ CF 10 wt\% & a 17.9 \(\pm\) 0.5 & a 2.6 \(\pm\) 0.07 & a 26.0 \(\pm\) 0.9 & b 1.6 \(\pm\) 0.07 * \\ CF 20 wt\% & b,c 20.8 \(\pm\) 2.3 & a 3.0 \(\pm\) 0.1 & d 30.5 \(\pm\) 1.5 * & d 2.2 \(\pm\) 0.1 * \\ CWM 10 wt\% & a,b 19.0 \(\pm\) 0.9 & a 2.8 \(\pm\) 0.10 & c 28.2 \(\pm\) 0.8 * & b,c 1.6 \(\pm\) 0.07 * \\ CWM 20 wt\% & c 22.6 \(\pm\) 0.7 * & b 4.0 \(\pm\) 0.09 * & e 33.4 \(\pm\) 0.8 * & d 2.2 \(\pm\) 0.05 * \\ CHM 10 wt\% & a 17.9 \(\pm\) 1.1 & a,b 3.3 \(\pm\) 0.09 * & b,c 28.2 \(\pm\) 0.3 * & c 1.7 \(\pm\) 0.03 * \\ CHM 20 wt\% & a,b 18.2 \(\pm\) 2.0 & a,b 3.4 \(\pm\) 0.08 * & c,d 30.5 \(\pm\) 1.3 * & d 2.0 \(\pm\) 0.1 * \\ \hline \hline \end{tabular}  
* Distinct letters indicate significant differences between samples by [PERSON]’s test,
* indicates a significant difference between matrix and treated fiber composites by [PERSON]’s test; CF: untreated curaua fibers; CWM: curaua treated with hot water and mercerized; CHM: curaua treated with hypochlorite and mercerized.  
\end{table} 
Table 2: Tensile and flexural properties for PHB and PLA composites reinforced with untreated and treated curaua fibers and neat PLA and PHB. of the curaua fibers, which provided a better adhesion between fiber/matrix, as reported by [PERSON] et al. [44]. Also, it is observed that the PLA matrix has no significant difference in Young's modulus compared to the CF 10 wt%. Figure 4 shows the fracture surface of the PLA polymer and the PLA-containing composites. In Figure 4C, it was observed that most of the curaua fibers in the studied region broke together with the PLA matrix, showing little detachment between the fiber and the matrix. This interface behavior demonstrated good adhesion, preceded by the fiber's treatment route. In the mechanical tensile tests, the curaua (treated with hot water and mercerized) 20 wt%/PLA presented the best results. This is because the curaua fiber used to produce this composite presented the best adhesion, which allowed the matrix to transfer the stresses received during the test to the fiber. The curaua fibers were mercerized and washed with sodium hypochlorite solution (Figure 4D), which resulted in a good dispersion of the fibers in the composite. However, the adhesion between the fiber and the matrix was low. Furthermore, it was observed that there was a large detachment of the fiber in the PLA matrix. Several pull-out failures were observed, which were responsible for the inferior mechanical behavior of these composites when subjected to tensile tests. Figure 4: SEM micrographs for PLA (**A**); composite containing 20% of curaua fibers (untreated) (**B**); composite containing 20% of curaua fibers (treated and mercerized) (**C**); composite containing 20% of curaua fibers (treated with chlorite and mercerized) (**D**). Comparing the unfilled PHB polymer with the PHB composites yielded the assumption that filling the PHB matrix with 10% curaua fibers does not relevantly improve the resistance against tensile or flexural stress.