## 3 Results and Discussion
### Differential Scanning Calorimetry (DSC)  
The phase transition temperatures and enthalpies of the neat PCMs and composite samples can be determined from the DSC thermograms shown in Figure 7, the main results of which are summarized in Table 3.  
The temperature range of melting is between 30 \({}^{\circ}\)C and 50 \({}^{\circ}\)C for all of the compositions. As expected, RT35 presents a lower melting point, even completing the phase transition before the start of RT44 melting. The MPA is the last to melt, with the entire transition occurring in the 45-50 \({}^{\circ}\)C range, slightly above that expected for this composition (61 wt.% myristic acid, 39 wt.% palmitic acid) [43].  
RT44 shows an extraordinary high melting enthalpy (270 J/g), RT35 has an intermediate value (236 J/g), and the lowest value belongs to MPA (196 J/g). This last material, obtained by mixing two fatty acids, benefits from a tuned melting enthalpy, reduced with respect to its neat precursors. However, it suffers from melting enthalpy reduction as a consequence of the mixing of its precursors.  
RT44 presents a double peak in melting, probably corresponding to two distinct stable molecular weight fractions, with C22 predominating [44]. When cooling, this separation appears even more evident, with the second peak at 39 \({}^{\circ}\)C being very sharp. Likewise, RT35 presents a double crystallization peak with a very similar shape to that of RT44, shifted to lower temperatures and with closer peaks. This peak separation can be attributed to the crystallization of the more mobile fraction of PCM (first peak), which acts as a nucleating site for crystallizing the remaining molecules [35]. MPA does not present any peak separation, even if a shoulder can be noticed in crystallization.  
EG enhances the PCM thermal response anticipating the phase transition, even if the scanning rate was selected to minimize this effect. RT35/EG14 exploits the melting enthalpy coherent to the expected value, while RT44/EG14 and MPA/EG14 shows around  
\begin{table}
\begin{tabular}{c c c c} \hline
**Sample** & \(T_{5\%}\) & \(T_{peak}\) & \(m_{700}\) \\  & [\({}^{\circ}\)**C]** & [\({}^{\circ}\)**C]** & [wt.\%] \\ \hline RT35 & 204.5 & 269.3 & 0.0 \\ RT35/EG14 & 195.3 & 261.5 & 12.5 \\ RT44 & 219.5 & 281.7 & 0.0 \\ RT44/EG14 & 217.8 & 284.0 & 10.7 \\ MPA & 223.2 & 299.8 & 0.0 \\ MPA/EG14 & 204.3 & 268.8 & 12.9 \\ \hline \end{tabular} \(T_{5\%}\) = temperatures associated with a mass loss of 5 wt.%; \(T_{peak}\) = temperatures associated with the maximum degradation rate; \(m_{700}\) = residual mass at 700 \({}^{\circ}\)C.  
\end{table}
Table 2: TGA results.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Sample** & \(T_{m1}\) & \(\Delta H_{m1}\) & \(T_{c}\) & \(\Delta H_{c}\) & \(T_{m2}\) & \(\Delta H_{m2}\) & \((PCM_{m2}^{\mathit{eff}})\) & \(\eta_{m2}\) \\  & [\({}^{\circ}\)**C]** & [**J/g**] & [\({}^{\circ}\)**C]** & [**J/g**] & [\({}^{\circ}\)**C]** & [**J/g**] & [**wt.\%] & [**wt.\%]** \\ \hline RT35 & 37.5 & 234 & 36.2–36.7 & 234 & 37.4 & 236 & 100 & 100 \\ RT35/EG14 & 37.3 & 204 & 35.6–32.7 & 206 & 37.2 & 206 & 87.4 & 99.7 \\ RT44 & 42.7–45.2 & 272 & 44.2–39.9 & 270 & 45.2–42.8 & 270 & 100 & 100 \\ RT44/EG14 & 42.8–45.4 & 221 & 43.8–37.7 & 219 & 45.4–42.6 & 220 & 81.5 & 92.9 \\ MPA & 48.6 & 193 & 45.2 & 196 & 48.5 & 196 & 100 & 100 \\ MPA/EG14 & 47.7 & 166 & 44.9 & 155 & 47.6 & 159 & 81.1 & 92.5 \\ \hline \end{tabular}
\end{table}
Table 3: DSC results.  
93% of the theoretical enthalpy. A possible explanation could be a local inhomogeneity of the impregnation, with a higher graphite content in the scanned specimens in comparison with the nominal composition.  
Figure 7: DSC thermograms of the neat PCM and PCM/EG systems at 1 \({}^{\circ}\)C/min: first heating (**a**), cooling (**b**), and second heating (**c**).