## 3 Results and Discussion
In order to increase the TES efficiency of these materials, milder processing conditions should be utilized in the future to retain the structural integrity of the microcapsules. Figure 4: (**a**) TGA and (**b**) DTG curves from thermogravimetric analysis of the prepared 3D samples. In sports applications or whenever a material is subjected to cyclic/vibrational load conditions, it is crucial to evaluate its viscoelastic behavior, which can be described through DMA tests in terms of storage modulus (E') and loss tangent (tan \(\delta\)). In Figure 6a,b, the E' and tan\(\delta\) curves of the 3D-printed samples are shown, while in Table 2, the main results are summarized (the loss modulus (E') curves are not reported for the sake of brevity). According to Figure 6a, at temperatures lower than \(-30\)\({}^{\circ}\)C, there is a trend of a decrease in the storage modulus with a decrease in the microcapsule content, while this trend is the opposite at higher temperatures. Furthermore, from Figure 6b, it can be noticed that the intensity of the tan\(\delta\) peak decreases in tandem with the microcapsule content due to the lower TPU amount in the formulation. The storage modulus increased upon introducing MWCNTs in the temperature range considered; at room temperature, E' moves from 6.1 MPa for neat TPU up to 9.2 in the TPU_1 MWCNT sample. Damping properties are influenced by the presence of microcapsules; in fact, the tan\(\delta\) peak at the TPU glass transition temperature decreased from the value of 0.80 for the neat TPU to 0.56 and 0.50 with M6D concentrations of 30 wt% and 40 wt%, respectively. The MWCNTs were able to slightly increase the glass transition temperatures compared to the neat TPU, while the microcapsules' introduction did not seem to substantially influence the Tg values, as already reported in the previous paper written by our group [34]. Furthermore, the incorporation of microcapsules inside the TPU matrix resulted in a shoulder in the E' and tan\(\delta\) curves located at about 10\(-\)15 \({}^{\circ}\)C, with a magnitude that increases in tandem with the M6D content. This signal is related to the melting of the paraffin wax within the microcapsules. It is thus clear that the viscoelastic response of these materials near ambient temperature could be strongly influenced by the melting of the paraffin inside the capsules. \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline  & \(\mathbf{T_{g}}\) & \(\mathbf{T_{n}}\) & **Melting Enthalpy** & **Relative Melting** & **T\({}_{c}\)** & **Crystallization** & **Relative** \\  & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) & (\({}^{\circ}\)C) \\ \hline TPU & \(-48.9\) & & - & & - & - & - \\ TPU\_30M6D * & 6.6 & 45.6 & 28.8 & \(-8.6\) & 42.1 & 26.6 \\ TPU\_30M6D\_0 SMVCNT & \(-4.4\) & 27.0 & 17.0 & \(-1.1\) & 29.1 & 18.4 \\ TPU\_30M6D\_1 MVCNT & \(-50.5\) & 5.1 & 32.8 & 20.7 & \(-2.1\) & 37.4 & 23.6 \\ TPU\_40M6D & 8.0 & 56.1 & 35.4 & \(-10.1\) & 52.6 & 33.2 \\ TPU\_40M6D\_0 SMVCNT & \(-5.4\) & 48.7 & 30.7 & \(-2.6\) & 54.2 & 34.2 \\ TPU\_40M6D\_1 MWCNT & \(-53.9\) & 6.4 & 47.6 & 30.0 & \(-2.0\) & 54.1 & 34.2 \\ M6D* & 5.0 & 158.5 & 100.0 & \(-9.4\) & 158.4 & 100.0 \\ \hline \hline \end{tabular}
* Results from DSC tests reported in [34].  
\end{table} 
Table 1: Results of DSC tests on the prepared 3D printed samples. Figure 5: DSC thermograms of the prepared 3D-printed samples. (**a**) First-heating and (**b**) -cooling thermograms. Quasi-static tensile tests are important when evaluating the effect of microcapsules and MWCNTs in addition to the mechanical behavior of 3D-printed materials.