Electron tunneling in carbon nanotubes and carbon black hybrid filler‐filled natural rubber composites: Influence of non‐rubber components

Filled natural rubber (NR) vulcanizates with various carbon based fillers, namely carbon nanotubes (CNTs), conductive carbon black (CCB) and CNT/CCB hybrid filler, were prepared with different types of rubber, namely epoxidized natural ruber (ENR), deproteinized NR (DPNR), and isoprene rubber (IR). The main aim was to examine the effects of polarity and non‐rubber components in rubbers on electrical conductivity and dielectric properties of the rubber composites. It was found that the phospholipids in NR molecules play an important role in controlling content of bound rubber and its layer thickness. This might be attributed to the cation‐π interactions of the phospholipid moieties with CNT and CCB sidewalls. Thus, the bound rubber layers in ENR and IR vulcanizates are very thin due to low phospholipid content in ENR and the absence of non‐rubber constituents in IR. On the other hand, thicker bound layers were observed in the filled NR and DPNR vulcanizates owing to their similar high phospholipids contents. Therefore, ENR and IR composites exhibited very low percolation threshold concentration due to the thin layer of electrically insulating bound rubber. Furthermore, analysis of variance indicated that addition of CCB into the CNT composites significantly improved the percolation, optimal conductivity and dielectric properties. POLYM. COMPOS., 39:E1237–E1250, 2018. © 2018 Society of Plastics Engineers