## 3 Results and Discussion
The UV-exposed PLA sample was the only one to deteriorate before reaching 100 \({}^{\circ}\)C. When composted samples were tested for pure PLA and the L10 composite, no deterioration in properties was obtained. For the L20_CO sample, both the storage modulus and the loss modulus decreased steadily and dropped by 15% compared to the nondegraded L20. A very high decrease was recorded for the wool composites, indicating a very high degradation of these composites in the ground. For the composted samples, there is a clear difference between the flax and wool composites, which have significantly lower properties. The TG curves and the corresponding DTG curves are presented in Figure 7. A summary of the most important parameters determined from the TG curves to assess the dynamics of material degradation is included in Table 3.  
From Figure 7, it can be seen that the manufactured composites show high thermal stability. The greatest difference can be seen for sample W10_CO, where degradation occurs significantly earlier than for the other samples (Figure 7e). In Table 3, it can be seen that much higher residue values at 600 \({}^{\circ}\)C were obtained for the samples with natural fibres. The degradation under UV light accelerated the weight loss in the samples with flax; this is due to the strong destruction of the matrix, which accounted for 90% of the weight of the composites. For wool fibres in the case of composting, no differences can be seen at first; they only appear around 350 \({}^{\circ}\)C, where the fibres play a significant role in the acceleration of degradation. For flax fibres with PLA, rapid changes occur from about 300 \({}^{\circ}\)C, where the degradation of the polymer itself begins, and the presence of fibres shifts the temperature of maximum degradation towards higher values [17]. PLA samples reinforced with other plant fibres (coir, pineapple leaves, and bamboo) also showed stability in the same temperature range, and from about 350 \({}^{\circ}\)C, they degraded in one step [36; 37]. The TG studies showed that the presence of both flax and wool fibres increased the degradation under UV light and during composting. A DSC study was carried out on PLA, L10, and W10 samples to assess the effect of the presence of the fibre on the processing and degradation properties of the polymer. Plots of the first- and second-cycle heating curves are shown in Figure 8, and a summary of the most important parameters analysed is given in Table 4. Additionally, the glass transition temperature value from the analysis of the DMA curves (Figure 6), calculated as a peak in the tan(\(\delta\)) plot, is added to the table for comparison. Figure 7: Comparison chart of TG and DTG curves: (**a**) TG curve of PLA samples, (**b**) DTG curve of PLA samples, (**c**) TG curve of L10 samples, (**d**) DTG curve of L10 samples, (**e**) TG curve of W10 samples, and (**f**) DTG curve of W10 samples. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Sample** & **T\({}_{\text{15\%}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{35\%}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{5\%}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{20\%}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{50\%}}\) (\({}^{\circ}\)C)** & **T\({}_{\text{DTGmax}}\) (\({}^{\circ}\)C)** & **W\({}_{\text{r}}\) (\%)** \\ \hline PLA & 288 & 309 & 318 & 342 & 359 & 367 & 0.53 \\ L10 & 266 & 301 & 310 & 334 & 351 & 358 & 2.17 \\ W10 & 239 & 292 & 305 & 330 & 348 & 357 & 4.16 \\ PLA\_UV & 267 & 307 & 317 & 343 & 360 & 367 & 0.57 \\ L10\_UV & 155 & 271 & 296 & 329 & 348 & 355 & 2.46 \\ W10\_UV & 235 & 289 & 305 & 331 & 349 & 358 & 3.58 \\ PLA\_CO & 290 & 311 & 318 & 338 & 353 & 358 & 0.99 \\ L10\_CO & 285 & 311 & 319 & 340 & 356 & 361 & 2.31 \\ W10\_CO & 237 & 275 & 287 & 315 & 334 & 341 & 5.11 \\ \hline \hline \end{tabular}  
* T\({}_{\text{15\%},\text{20\%}}\) temperature at 1, 3, 5, 20, and 50% mass loss; T\({}_{\text{DTGmax}}\)—degradation temperature; W\({}_{\text{r}}\)—char residue at 600\({}^{\circ}\)C.  
\end{table} 
Table 3: Results of TG analysis *.