Evolution of Morphological, Electrical, Thermal, and Mechanical Properties of Elastomer Nanocomposites With Different Sizes of MWCNTs

Abstract

Ethylene-propylene-diene-monomer (EPDM) nanocomposites with three various types of multiwall carbon nanotubes (MWCNTs) were fabricated to investigate the size effect of MWCNTs on the morphological, electrical, thermal, mechanical, and viscoelastic properties, as well as swelling ratio and crosslinking density. MWCNTs enhance electrical, thermal, mechanical, and viscoelastic properties regardless of MWCNT size. The MWCNT size is vital in determining percolation thresholds and thermal conductivity; however, it considerably influences the electrical conductivity in only the percolation threshold region (2–10 phr). In addition, the diameter of MWCNTs is a more regulating factor for nanocomposites' electrical properties than length. The EPDM nanocomposites, including MWCNTs with a longer length, low diameter, and higher specific surface area (SSA), show a better thermal conductivity enhancement (95%) due to forming more easily thermally conductive networks. The size of MWCNTs is a negligible key factor for mechanical and viscoelastic properties. With increasing MWCNT contents, the swelling ratio decreases, and crosslinking density increases. MWCNTs with lower diameter, length, and higher SSA exhibit less enhancement in all mentioned properties of EPDM-based nanocomposites due to worse dispersion in the matrix.