Structural variations and morphological features of polyethylene/carbon black conductive composites after processing in an internal mixer



Polyethylene (PE) composites filled with carbon black (CB) were prepared using an internal mixer. Several analytical techniques, including rheometry, gel permeation chromatography, electrical conductivity measurements, differential scanning calorimetry, wide-angle X-ray diffraction, and transmission electron microscopy (TEM), were used to reveal the structural variations, thermal degradation, morphological features, and crystallization of the PE/CB conductive composites. It was found that the PE polymer chains were degraded, forming long-chain branching structures after over 30 min of internal mixing. The electrical conduction of the PE/CB composites was determined by the filler content and distribution. The electrical percolation threshold of the PE/CB composites was determined to be between 20 and 30 wt %. The addition of CB had no significant influence on the crystallinity of the PE/CB composites. In contrast, the electron-beam radiation dose had a significant effect on crystallinity. TEM micrographs of the PE/CB composites exhibit a random four-phase morphology, including PE lamellae, PE amorphous, CB particles, and voids at the PE/CB interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1038-1046, 2013