## 3 Results
### Thermogravimetric Analysis (TGA) and Different Scanning Calorimetry (DSC) of Curua/Composites  
The composites were thermally characterized by TG-DTG analysis. Figure 5 shows the TG and DTG curves for neat PLA, PHB, and its composites with curua fiber. The PLA curves obtained after the extrusion process (Figure 6A) matrix showed thermal stability up to 290 \({}^{\circ}\)C and only a weight loss stage corresponding to its degradation, which starts at 290 \({}^{\circ}\)C and reaches a higher degradation rate at 360 \({}^{\circ}\)C [46]. At the final analysis temperature, at 500 \({}^{\circ}\)C, the PLA matrix presented a small portion of residues, around 1.5%. Similar thermal behavior of PLA degradation was observed for this study [47], where neat PLA samples did not go through the extrusion process. Curua/PLA composites showed the same thermal behavior as neat PLA with only one stage of degradation; however, all composites showed a reduction in thermal stability. According to the DTG image (see Figure 6A), it is noted that the CWM 20 wt%/PLA and CHM 20 wt%/PLA showed the same degradation peak temperature at 340 \({}^{\circ}\)C. However, the CWM 20 wt%/PLA occurred more slowly and started at a lower temperature. The PLA matrix showed a degradation peak at 360 \({}^{\circ}\)C, referring to the thermal degradation of this polymer, which, according to [PERSON] et al. [48], occurs between 350 and 370 \({}^{\circ}\)C.  
Also, all composites had a lower degradation peak temperature than the PLA matrix. Still, in a larger temperature range, this was because the fiber and the polymer degradation temperature were close; however, when the fiber degradation is lower, the composites started degradation at temperatures lower than the pure polymer, degrading the fiber first and following the polymer degradation, which resulted in a greater degradation range than for the pure polymer. Figure 6B below shows the TGA and DTG curves for PHB and composites. It shows that the thermal behavior of PHB and composites is similar. PHB has its highest decom  
Figure 6: Comparative TG and DTG curves of untreated and treated curaua fibers with different percentages in PLA matrix (**A**) and PHB matrix (**B**). CF: untreated curaua fibers; CWM: curaua treated with hot water and mercerized; CHM: curaua treated with hypochlorite and mercerized. position speed at a temperature of 292 \({}^{\circ}\)C. In the composites, this temperature is slightly higher because the amount of fiber in the composite moves the polymer's peak to a higher temperature due to the decomposition of the fibers starting around 300 \({}^{\circ}\)C and the bonding established between the reinforcement and matrix. When evaluating composites, we see that all have two stages of degradation. The first, at about 300 \({}^{\circ}\)C, refers to PHB degradation [49]. In comparison, the second at around 330 \({}^{\circ}\)C is due to the degradation of the curaua fiber, more specifically, the alpha-cellulose present in the fiber [50]. In Figure 6B, verifying the degradation speed of the composites is possible. The degradation rate of pure PHB is the highest since, at 292 \({}^{\circ}\)C, the whole polymer decomposes at once. All the connections between the macromolecules are broken, and the material degrades. When the fibers are added to the polymer, they promote a delay in the decomposition of the polymer because the two are linked. The composite has a high degradation temperature as the fibers resist temperatures higher than the polymer. That is, the fibers promote an increase in the thermal stability of the polymer [51]. To corroborate this statement, the curve shows that the higher the fibers contained in the composite, the lower its decomposition speed. For composites with 20%, the decomposition speed is lower than in composites with 10% by the weight of fibers. The trend is that an increase in the composite fibers leads to a decrease in the polymer's degradation, thus improving its thermal stability.