## 3 Results
### Thermomechanical Performance of the Green Composite Pieces  
Table 5 shows the VST and HDT values of the injection-molded pieces of neat PLA and PLA/TCHF, which are important thermomechanical parameters that can be used to estimate their upper useful temperature limit for uses in, for instance, packaging or disposables. VST, which reflects the material's softening by temperature rises, increased progressively from 56.6 \({}^{\circ}\)C, for neat PLA, to 59.9 \({}^{\circ}\)C, for PLA/50 TCH, respectively, following an evolution similar to that found in hardness. This result is in agreement with the study of [PERSON] et al. [52], who showed that the VST of HDPE increased with the loading of coffee husk fiber (CHF), which was attributed to a fiber \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Piece** & **T5\% (\({}^{\circ}\)C)** & **T\({}_{\text{deg}}\) (\({}^{\circ}\)C)** & **Residual Mass (\%)** \\ \hline CHF & \(237.8\pm 1.2\) & \(360.6\pm 2.2\) & \(25.2\pm 0.3\) \\ TCHF & \(252.1\pm 1.3\) & \(357.8\pm 1.3\) & \(39.6\pm 0.3\) \\ PLA & \(320.4\pm 2.3\) & \(347.4\pm 1.4\) & \(5.6\pm 0.3\) \\ PLA/20 CHF & \(298.9\pm 1.6\) & \(351.1\pm 2.2\) & \(3.2\pm 0.6\) \\ PLA/20 TCHF & \(322.4\pm 1.7\) & \(354.7\pm 2.2\) & \(5.6\pm 0.5\) \\ PLA/30 TCHF & \(306.0\pm 1.3\) & \(347.7\pm 1.7\) & \(8.1\pm 0.4\) \\ PLA/40 TCHF & \(299.8\pm 1.8\) & \(343.5\pm 1.8\) & \(9.7\pm 0.7\) \\ PLA/50 TCHF & \(301.1\pm 1.3\) & \(341.4\pm 1.6\) & \(10.9\pm 0.8\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main thermal degradation parameters of the injection-molded pieces of polylctide (PLA) with coffee husk flour (CHF) and torrefied coffee husk flour (TCHF) in terms of temperature at mass loss of 5 % (T5%), degradation temperature (Tdeg), and residual mass at 700 \({}^{\circ}\)C.  
Figure 6: **(a)** Thermogravimetric analysis (TGA) and **(b)** first derivate thermogravimetric (DTG) curves of the injection-molded pieces of polylctide (PLA) with coffee husk flour (CHF) and torrefied coffee husk flour (TCHF). reinforcement that prevented deformation of the composites. Concerning HDT, the values evolved in a similar manner to VST, showing a slight and progressive increase from 51 \({}^{\circ}\)C, for neat PLA, to 54.1 \({}^{\circ}\)C for PLA/50 TCHF. This enhanced thermomechanical resistance can be attributed to the higher modulus and amount of crystallinity, since both parameters increased with increasing TCHF content. Similar results were obtained by [PERSON] et al. [72], who showed that the softening point of PBAT/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) blends increased up to 3 \({}^{\circ}\)C with the incorporation of CSS. Finally, Figure 7 shows the mechanical performance of the green composite pieces under dynamic load conditions as a function of temperature. Figure 7a displays the evolution of the storage modulus with temperature. In the temperature range between 30 and 50 \({}^{\circ}\)C, below the glass transition region, the incorporation of TCHF produced an increase in the storage modulus of PLA. This behavior indicates that the addition of the TCHF filler led to a stiffer material since the lignocellulosic particles restricted the biopolymer chain mobility and also promoted crystallization as described above during the thermal characterization. From approximately 55 \({}^{\circ}\)C, a prominent decrease in the storage modulus due the glass transition process can be seen [41]. In addition, from nearly 90 \({}^{\circ}\)C, an increment in the storage modulus was detected. This phenomenon is associated with the cold crystallization of PLA. During this process, the biopolymer chains reorganize into a more compact structure, leading to an increase in the storage modulus [73]. Furthermore, as more TCHF powder was added, in agreement with the previous DSC analysis, a slight decrease in the cold crystallization temperature was noticed. Figure 7b displays the evolution as a function of temperature of the damping factor (_tan_\(\delta\)) for the unfilled PLA piece and the PLA/TCHF composite pieces.