Melt spinning of conducting polymeric composites containing carbonaceous fillers

Abstract

Fibers produced by melt spinning of conductive polymer composites are attractive for several applications; the main drawback is however reduced processability at high filler concentrations. Carbon nanotubes (CNTs) are considered suitable fillers for conductive polymer composites, replacing conductive grades of carbon black (CB). In this study, the fiber-forming properties of conductive polymer composites based on a conductive grade of CB and two masterbatches with CNT in a polyethylene matrix were investigated. The CB was also used in a polypropylene matrix for comparison. The rheological properties of the filler-containing melts in shear and their extensional behavior were evaluated. A piston-driven device was used to extrude the molten materials through a capillary; different capillary geometries were tested. Fibers were produced at various draw ratios, and their conductivity was determined. To assess the ultimate extensibility, a modified Rheotens method was used. The results showed that a conductive CB grade can have a lower percolation threshold and higher conductivity than a material with CNT. Conductivity decreased with increasing melt draw ratio for both types of fillers. The spinnability of the materials decreased with increasing concentration of filler material and correlations were found between spinnability and melt elasticity.

Electrically conductive polymeric bi‐component fibers containing a high load of low‐structured carbon black

“…The present system had a critical exponent β of 2.4, somewhat larger than the stated range. In our previous studies using a CB with a substantially higher surface area, a similar value of β (2.3) was found, but a value as high as 2.9 was recently reported for CB/HDPE systems …”

“…Thus, there are good arguments for seeking other ways of making textile fibers conductive. Our research group has recently investigated the possibility of using conductive polymer composites in the manufacturing of melt‐spun textile fibers . Conductive carbon nanoparticles, carbon black (CB), carbon nanotubes (CNT) and, recently, graphite nanoplatelets (GNP), have gained intense attention during the last decades.…”

“…With CNTs in a fiber, the cylindrical CNTs will be oriented in the axial direction of the fiber . Consequently, the conductivity of the fibers is reduced with increasing draw‐down ratio . Thus CB, although its lower inherent conductivity compared to CNT and GNP, would be the most favourable option for melt spinning applications since it is less affected by flow orientation effects.…”

Effect of carbon black on electrical and rheological properties of graphite nanoplatelets/poly(ethylene-butyl acrylate) composites

“…The correlation between the two thresholds is quite reasonable for the HS-CB/GNP systems considering the difference in orientation between the specimens. Strååt et al [23] reported a good agreement between the electrical and the rheological thresholds in the case of PP and PE containing the same type of high-structured CB as used in this study. The conductivity measurements reported in this case [23] were also performed using extruded strands.…”

“…The conductivity corresponding to the plateau value approached at higher filler contents was several orders of magnitude higher for the CB composites than for those containing GNP. In the work of Strååt et al [23] the same kind of CB was mixed with both polypropylene (PP) and high density polyethylene (HDPE) and despite the fact that both processing and electrical measurements were conducted in a similar manner as in the present work, they report a lower percolation threshold for both polymer systems, being of the order 1 vol%. The percolation threshold of 6.9 vol% (15 wt%) found in this work for the pure melt mixed GNP composite is rather low compared to published results.…”