# Thermal and Mechanical Behavior of Elastomers Incorporated with Thermoregulating Microcapsules
## 3 Results and Discussion  
### Elastomer Synthesis  
A total of 10 different elastomers were produced as result of varying the [NCO]/[OH] molar ratio and the mSD-(LDPE-EVA-RT27) content.  
The composites were synthesized with [NCO]/[OH] molar ratios of 1.05 and 1.1 while varying the mSD-(LDPE-EVA-RT27) content within 0.0-20.0 wt.%. The composite names include all this information by putting after the letter E (corresponding to elastomer) the [NCO]/[OH] molar ratio and the mSD-(LDPE-EVA-RT27) content, separated by dashes. The names and values of both variables for the different synthesized elastomers are gathered in Table 1.  
All the formulations allowed successful synthesis of the elastomers, as can be seen in Figure 1.  
At a simple view, the elastomers reagents successfully reacted. However, in order to confirm the formation of the characteristics of the elastomers' structures, FTIR analyses of the composites with different mSD-(LDPE-EVA-RT27) contents and [NCO]/[OH] molar ratios were carried out (Figure 2).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Name** & **[NCO]/[OH]** & **mSD-(LDPE-EVA-RT27) (wt.\%)** \\ \hline E-1.05-0 & & 0.0 \\ \hline E-1.05-5 & & 5.0 \\ \hline E-1.05-10 & 1.05 & 10.0 \\ \hline E-1.05-15 & & 15.0 \\ \hline E-1.05-20 & & 20.0 \\ \hline E-1.1-0 & & 0.0 \\ \hline E-1.1-5 & & 5.0 \\ \hline E-1.1-10 & 1.1 & 10.0 \\ \hline E-1.1-15 & & 15.0 \\ \hline E-1.1-20 & & 20.0 \\ \hline \end{tabular}
\end{table}
Table 1: [NCO]/[OH] molar ratios and mSD-(LDPE-EVA-RT27) contents of the synthesized elastomers.  
The presence of urethane groups in the synthesized elastomers can be clearly identified in Figure 2 by the stretching vibrations of the -NH bonds around 3360 cm\({}^{-1}\)[17]. Aside from that, the characteristic signals of the carbonyl groups (-C=O), hydrogen bonds, -NH bending vibrations and -CN stretching vibrations appeared at 1727, 1700, 1527 and 1306 cm\({}^{-1}\), respectively [18]. The -NH groups could join the -C=O by the hydrogen bonds in the hard segments and with the -C-O-C of the soft segments. The peaks at 2935 cm\({}^{-1}\) and 2837 cm\({}^{-1}\) correspond to the symmetric and asymmetric stretching vibrations of -CH\({}_{2}\) group, respectively, while at 1373 cm\({}^{-1}\) and 1456 cm\({}^{-1}\), bending stretching in the polyol chain appeared [19]. In addition, the lack of significant stretching vibrations of the isocyanate group (N=C=O) of MDI at 2300 cm\({}^{-1}\) confirmed the success of the reaction for the case of a [NCO]/[OH] molar ratio of 1.05 [20]. On the contrary, that signal appeared for the case of a [NCO]/[OH] molar ratio of 1.1, indicating the excess of isocyanate groups for the case of this formulation. On the other hand, the existence of a peak at 1594 cm\({}^{-1}\) indicated the presence of aromatic groups coming from MDI [18]. Finally, the peaks that appeared at 1165, 1138 and at 1078 cm\({}^{-1}\) corresponded to the stretching and bending vibrations of C-O-C present in the ether, urethane and ester groups of the elastomers, respectively [18].  
Figure 1: Appearance of the synthesized elastomers with different [NCO]/[OH] and mSD-(LDPE:EVA-RT27) contents.  
Figure 2: FT-IR spectrums of the synthesized elastomers with different mSD-(LDPE:EVA-RT27) contents and [NCO]/[OH] values of (**a**) 1.05 and (**b**) 1.1.