Effect of polymeric ratio in matrix and blending sequence on electrical resistivity of carbon black-filled multi-phase composites

Electrically conductive polymer composites (CPCs) with significant conductivity improvements were easily achieved by loading plenty of conducting fillers, but that goes against the original advantages. Thus, the filler loading needed to be controlled as little as possible in CPCs with the guarantee of electrical conductivity. This work investigated the effect of polymeric matrix ratio and blending sequence on conductivity and mechanics, and the studied conductive biphasic composites polypropylene (PP)/styrene-butadiene-styrene tri-block copolymer (SBS)/carbon black (CB) were prepared by melting blending with only 2-vol% filler loading. Three variational volume ratios of PP:SBS were 30:70, 50:50, and 70:30. And a two-step method was applied to prepare the filled composites with regulatory filler locations that contained three mixing sequences: two components were initially mixed and then the third component from PP, SBS, and CB was added. The blending sequence premixing PP and CB displayed superiority in conductivity improvement with the volume resistivities of 1.46 × 10⁴ Ω m and 2.15 × 10⁵ Ω m for PP:SBS = 50:50 and 70:30, respectively, as the higher PP content ensured better phase continuity contributing to conductive network construction, which was confirmed by the rheology behaviors and CB distribution state. Besides, the measured mechanical properties illustrated that the CPCs with high contents of the elastomer SBS possessed better tensile performances, potentially adopted in the application with medium deformation.