Carbon Black-Filled Conductive Polymers of Polypropylene, Ethylene Vinyl Acetate Copolymer, and Their Ternary Blends

Abstract

The objective of this study was to investigate the electrical conductivity of polypropylene (PP)/Carbon Black (CB) blends, Ethylene-Vinyl Acetate (EVA)/CB blends, and ternary blends of PP, EVA, and CB. PP/CB and EVA/CB blends were prepared in a Haake rheometer. Both volume and surface resistivities of PP/CB blends showed a percolation around 4 wt % CB. PP/EVA/CB blends were made by compounding a 30/70 CB/EVA blend with PP in a Brabender twin screw extruder to maintain a constant ratio between EVA and CB. The conductivity of PP/EVA/CB samples showed a dependence on processing history. Both volume and surface resistivity of the samples extruded once showed only a small decrease between 3 and 7.5 wt % CB. After three extrusions the resistivity of 3 wt % CB increased substantially and the resistivity of 7.5 wt % CB decreased slightly. The samples extruded three times had a lower standard deviation. Calculated surface tension indicated that CB preferentially distributed in EVA phase.Multiple pass in the twin screw extruder decreased phase size and accounted for the change of resistivity.

Dielectric Spectroscopy of Anisotropic Polypropylene/Nylon‐66 Blends Containing Carbon Black

“…g B ) 0.5 of polymers at the processing temperature [24] 0.056 [24] CB 4.37 Ny 31 [22] 0.065 [22] CB, PP 0.27, 2.45 CB 42 [23] 0.075 [24] Dielectric Properties of PP and NY blends However, in the latter blend at low frequencies a short range of constant conductivity was also observed when measuring in the perpendicular to the flow direction. Thus, this blend, having a CB volume fraction of 0.019, appears to represent a composition of a transitional behavior, namely, from almost linear dependence of conductivity on frequency to the behavior observed when measurements were performed in the flow direction, i.e., constant conductivity below a critical frequency above which the conductivity increases.…”