## 4 Conclusions  
The effect of SWCNTs on the vulcanization process of the NR using organic peroxides was analyzed. NR composites filled with SWCNTs show a notable reduction in the _t.v._ values when compared with the neat NR composites and the NR-CB composites; this is associated with the presence of free radicals generated by thermal decomposition. We suggest that the concentration of the free radicals was increased by the high thermal conductivity of the SWCNTs. The mechanical properties of the NR composites vulcanized with different cross-linking agents exhibit increases in tensile strength, moduli, tear strength, and hardness of up to 75, 83, 27, and 10%, respectively, when the SWCNTs are used as filler in the NR composites. The lower values of strain at breakage for the NR-SWCNTs composites obtained through the vulcanization with organic peroxides suggest that the C-C bonds formed during the process promote the formation of more rigid polymer networks. The evaluation of the degree of vulcanization by the calculations of \(\overline{M_{c}}\) values confirms the improvement in the vulcanization for the NR-SWCNTs composites, mainly when organic peroxides are used as cross-linking agents. The analysis by Raman spectroscopy indicates the interactions between nanotube walls, free radicals, and reactive chemical species during the vulcanization process, which introduce defects that increase the disorder (D-band) and reduce the semiconductor character (G-band) of the SWCNTs. From the experimental findings obtained for the NR composites developed in the present work, it is possible to confirm that the incorporation of SWCNTs at a relatively low content (0.7 phr) in conjunction with the use of organic peroxides for the NR vulcanization represents a potential alternative to the traditional methods used for the improvement of the physicochemical properties of NR composites.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**NR-SWCNTs Composites** & **ID/IG Ratio** &
\begin{tabular}{c} **Frequency, \(\delta\)** \\ \([\delta_{G\text{ }_{\text{NR-SWCNTs}}}-\delta_{G\text{ }_{\text{SWCNTs}}}]\) (cm\({}^{-1}\)) \\ \end{tabular} \\ \hline SWCNTs (pristine) & 0.2452 & 0 \\ NR-S-SWCNTs & 0.3778 & 5 \\ NR-T29-SWCNTs & 0.3648 & 13 \\ NR-DCP-SWCNTs & 0.3195 & 16 \\ NR-T145-SWCNTs & 0.3520 & 17 \\ \hline \hline \end{tabular}
\end{table}
Table 7: \(I_{D}/I_{G}\) ratio of the NR-SWCNTs composites with different vulcanization agents.  
**Author Contributions:** Conceptualization, L.E.E. and A.E.-Z.; methodology, Y.V.-M. and L.E.E.E.; validation, Y.V.-M., C.A.R.-H., M.M., and L.E.E.; formal analysis, Y.V.-M., C.A.R.-H., M.M., and L.E.E.; investigation, Y.V.-M., C.A.R.-H., L.E.E., and A.E.-Z.; resources, L.E.E. and A.E.-Z.; data curation, Y.V.-M., C.A.R.-H., and L.E.E.E.; writing--original draft preparation, Y.V.-M. and L.E.E.; writing--review and editing, C.A.R.-H., M.M., and A.E.-Z.; visualization, Y.V.-M., C.A.R.-H., and L.E.E.; supervision, L.E.E. and A.E.-Z.; project administration, L.E.E. and A.E.-Z.; funding acquisition, L.E.E. All authors have read and agreed to the published version of the manuscript.  
This research was funded by CONACYT through the project 61061.  
Not applicable.  
We dedicate this manuscript in memory of [PERSON] for his invaluable contribution and help towards the culmination of this work. We also fondly remember his kindness and friendship. Also, the authors acknowledge to [PERSON], [PERSON] and [PERSON] for the technical support in the analytical characterization.  
The authors declare no conflict of interest.