The use of composites in various industries had significantly increased in recent decades. In composite structures subjected to thermal and mechanical loads, microcracks could lead to leakage and failure. To prevent this issue, sealing the structures with coating sealants and polymeric and elastomeric films was essential. These materials were resistant to gas permeation and thermal shocks. In this research, the properties of silicone nanocomposites were improved by adding nanoclay (Cloisite 5) and modifying its surface using APTES (silane agent). The results of TGA, XRD, and FTIR tests indicated the bonding of aminosilane groups with hydroxyl groups in Cloisite, with a bonding percentage of 3.66%. Additionally, the morphological analysis of the nanocomposites showed that the presence of modified nanoclays led to improved dispersion and enhanced mechanical properties. Thermal degradation tests revealed that the modified nanoparticles could increase thermal stability. Furthermore, the surface modification of nanoclays contributed to better rubber curing and reduced permeability in silicone nanocomposites. The results of the time-sweep test indicated that the surface modification of nanoclays further improved the curing of this rubber. Overall, this research demonstrated the positive impact of modified nanoclays on the thermal and mechanical properties of nanocomposites, which could enhance their performance in industrial applications.