Effects of Multi-Walled Carbon Nanotubes and Conductive Carbon Black on Electrical, Dielectric, and Mechanical Properties of Epoxidized Natural Rubber Composites

The influence of multi-walled carbon nanotubes (MWCNTs) and conductive carbon black (CCB) on cure, electrical, dielectric, and mechanical properties of epoxidized natural rubber (ENR) composites was investigated. It was found that short MWCNTs (S-MWCNTs) with low loading significantly affected the cure characteristics in a way similar to high loading of CCB. Moreover, the ENR/S-MWCNTs composites exhibited high AC conductivity, dielectric constant, and dielectric loss tangent (tan delta) compared to the ENR/CCB and ENR/L-MWCNTs (long MWCNTs) composites. In addition, the S-MWCNTs composites showed the lowest percolation threshold concentration, defined as the lowest loading to form conductive paths in the insulating ENR matrix. This might be attributed to the comparatively high interfacial polarization, with good dispersion and distribution, of the S-MWCNTs in ENR matrix. These characteristics were confirmed by TEM imaging and by a high bound rubber content, corroborating strong filler-rubber interactions in the ENR/S-MWCNTs composites. However, the L-MWCNTs composites showed the lowest electrical and other related properties, despite the highest aspect ratio and specific surface area of this filler. This might be because of the flocculation of nanotubes by mutual entanglement, leading to a poor uneven distribution in the ENR matrix. (C) 2015 Society of Plastics Engineers