## 3 Results and Discussion
### Thermal Properties
#### 3.2.2 Calorimetric Characterization (DSC) and Kinetics Analysis of Crystallization  
It has been widely demonstrated that the physical behavior of PLA is highly influenced by its thermal properties. In particular, both the glass transition temperature and the crystallinity degree profoundly affect the mechanical properties of the resulting materials [10; 11]. In Figure 3a-c, DSC thermograms (first, heating-cooling; second, heating) on neat PLA and relative nanocomposites samples are reported, while in Table 3 the most significant results are summarized. The main signal of PLA was the \(T_{g}\) centered at around 60 \({}^{\circ}\)C, and only a small melting peak could be detected at around 140 \({}^{\circ}\)C [9]. In the cooling step at \(-\)10 \({}^{\circ}\)C/min, it was interesting to note the delay  
Figure 3: Differential scanning calorimetry (DSC) thermograms of neat PLA and relative nanocomposites at different nanosilica contents (2–24 vol%). (**a**) First heating; (**b**) cooling step; (**c**) second heating. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \(\mathbf{T_{g1}}\) & \(\mathbf{T_{m1}}\) & \(\mathbf{W_{c1}}\) & \(\mathbf{T_{gC}}\) & \(\mathbf{T_{g2}}\) \\  & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** & **(\%)** & **(\({}^{\circ}\)C)** & **(\({}^{\circ}\)C)** \\ \hline PLA & 59.6 & 141.2 & 0.6 & 57.0 & 59.4 \\ PLA-Ar805-1 & 59.7 & 140.8 & 1.2 & 53.7 & 60.0 \\ PLA-Ar805-2 & 60.4 & 141.2 & 1.0 & 53.8 & 59.9 \\ PLA-Ar805-4 & 58.8 & 140.5 & 1.2 & 51.5 & 59.7 \\ PLA-Ar805-5 & 59.9 & 140.8 & 1.5 & 51.0 & 60.8 \\ PLA-Ar805-16 & 58.9 & 139.9 & 1.2 & 54.4 & 60.0 \\ PLA-Ar805-24 & 56.6 & 139.1 & 1.5 & 50.1 & 59.7 \\ \hline \hline \end{tabular} T\({}_{g1}\) = glass transition temperature (first heating stage). T\({}_{gC}\) = glass transition temperature (forst heating stage). T\({}_{g2}\) = glass transition temperature (second heating stage).  
\end{table} 
Table 3: Results of DSC analysis of neat PLA and relative nanocomposites at different nanosilica contents (1–24 vol%). in \(T_{g}\) signal of fumed silica filled nanocomposites, as a consequence of the reduced mobility of polymer chain determined by the filler, and the total absence of any crystallization. In addition, in the second heating scan, the signal associated with the melting peak was only partially detectable at 140 \({}^{\circ}\)C, and an average \(T_{g}\) of 59.9 \(\pm\) 0.4 \({}^{\circ}\)C for FS nanocomposites could be determined. In our previous paper on cycloolefin copolymer (COC)-silica nanocomposites [28], a slight \(T_{g}\) increase was observed from DMTA analysis at elevated silica amounts. However, the observed \(T_{g}\) enhancement in that work was very limited (not more than 2 \({}^{\circ}\)C with a silica loading of 2 vol%). It is interesting to note how the \(T_{g}\) was not substantially affected by nanoslica introduction. Moreover, crystallizability, crystallinity degree (W\({}_{\rm c}\)), and melting temperature (T\({}_{\rm m}\)) did not seem to be affected by nanosilica addition. At a general level, it can be concluded that the thermal behavior of both neat PLA and of the relative nanocomposites samples is typical of an amorphous material. It is also important to consider that PLA-based materials are prone to long-time crystallization under certain environmental conditions, and either crystallizability or an optimal crystallization temperature of commercial PLA are crucial for the significant influence on the physical properties of the resulting products [63]. Therefore, a detailed analysis on the crystallization kinetics on the prepared samples could give interesting information about the role played by silica nanoparticles on the crystallization capability of PLA. With this aim, isothermal DSC tests were performed at different temperatures. In Figure 4a-d, crystallization kinetics investigation of PLA and PLA-Ar805-8 nanocomposite samples are reported. Figure 4: Crystallization kinetics of PLA and PLA-Ar805-8 nanocomposite samples.