Effects of the size and filler loading on the properties of copper‐ and silver‐nanoparticle‐filled epoxy composites

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.