<scp>PLA</scp>/<scp>CB</scp> and <scp>HDPE</scp>/<scp>CB</scp> conductive polymer composites: Effect of polymer matrix structure on the rheological and electrical percolation threshold

Abstract In this study, the effect of the polymer matrix structure on the rheological and electrical percolation threshold of polymer/carbon black (CB) conductive polymer composites (CPCs) was investigated. Poly(lactic acid) (PLA) and high‐density polyethylene (HDPE) were used as polymer matrices. Through rheological analyses, an increase in complex viscosity was observed with increasing CB concentration, accompanied by a reduction in the Newtonian plateau. Additionally, an increase in the solid‐like behavior was observed, suggesting the formation of a percolated network. The rheological percolation threshold was found to be 5.13% CB mass fraction for the PLA/CB composite and 10.72% for the HDPE/CB composite. Electrical conductivity results were fitted to the sigmoidal Boltzmann model, and its derivative was used to identify the electrical percolation threshold. For PLA/CB, this threshold was reached at 5.39% CB mass fraction, while for HDPE/CB, it occurred at 5.75%. Morphology analysis by scanning electron microscopy and atomic force microscopy indicated that the polymer matrix structure affected the distribution/dispersion of the CB particles within the polymer matrix. Highlights The effect of polymer matrix structure on polymer/CB CPCs was investigated. The crystallinity of the polymer matrix affected the percolation threshold. PLA/CB showed higher conductivity than HDPE/CB CPCs.