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In this work, the performance of polydimethylsiloxane (PDMS) nanocomposites with carbon black (CB) and multi-walled carbon nanotube (MWCNT) fillers was studied. The carbon nanofillers were first introduced in the solvent to promote an adequate dispersion. The silicone rubber was then reinforced with the carbon nanofillers by a mechanical mixing process followed by film casting. It was found that only small amount of MWCNTs is required to reach the percolation threshold that produces high electrical conductivity. Filler size and segregation, as observed by scanning electron microscopy, play important roles in determining the electrical properties of silicone elastomer filled composites. Transmission electron microscopy was also performed to examine the tube–tube interaction of MWCNT in silicone rubber. The MWCNT/PDMS nanocomposites have higher electrical conductivity value compared to the CB/PDMS nanocomposite. The percolation threshold for MWCNT/PDMS nanocomposites was approximately 1.0 vol% of MWCNT loading with a value of –4.06 log σ (S/cm). On the contrary, no obvious percolation threshold of CB/PDMS nanocomposites was observed, as the CB fillers added from 0.5 to 2.0 vol% in the PDMS. The MWCNT/PDMS nanocomposite also showed better thermal stability than the CB/PDMS nanocomposite. The onset temperature for 0.5 vol% of MWCNT/PDMS and CB/PDMS nanocomposites were 528°C and 492°C, respectively.

Copper-nanoparticle (CuNP)-filled nanocomposites were prepared with various particle sizes and loadings. The nanocomposites incorporating 20-nm CuNPs with 5 vol % loading displayed optimum properties as determined by electrical, mechanical, and thermal characterization. Silver nanoparticles (AgNPs) with a size of 20 nm were loaded into the epoxy resin to allow a comparison of the properties. Interestingly, at the percolation threshold, a 5 vol % loading of CuNP and AgNP nanocomposites resulted in slightly similar electrical conductivities of 0.01 and 0.02 S/cm, respectively. The CuNP and AgNP nanocomposites were also subjected to thermal aging at 150 C, and we observed that the electrical conductivity of both nanocomposites dropped only by about one order of magnitude after 8 weeks of exposure.

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