Fibres spun from thermoplastic poly(hydroxy ether of bisphenol A) filled with weight fractions of 1, 3, 6, 8 and 12 wt.% of multi-wall carbon nanotubes (MWCNTs) were prepared at elevated process temperatures using a three-roll-mill for homogeneous dispersion of the MWCNTs and a twin-screw compounder with an attached winding roll for fibre spinning. Production caused fibre draw down ratios (DDR) from 1 to a maximum of 54 resulting in fibre diameters from 0.7 mm down to 0.07 mm were used. The state of dispersion of the MWCNTs was characterized by transmission electron microscopy (TEM). The electrical resistivity of the fibres and the percolation threshold were obtained as a function of weight fraction of MWCNTs and the fibre draw down ratio. The effect on resistivity of a subsequent heat treatment at 180 °C and on dissolution of the fibre's outer layers were analysed when embedded in liquid epoxy resin. Percolation thresholds between 6 wt.% and 12 wt.% were estimated depending on the draw down ratio of the fibres. The observed lowest resistivity was about 5 Ωm for as spun fibres without drawing. It increases over several orders of magnitude to the limit of measurability with increasing the draw down ratio. It was further shown that the resistivity greatly reduced after heat treatment, as well as after embedding the fibres in epoxy resin due to the effect of near surface solubility of the thermoplastic fibre when in contact to the epoxy resin. A reduced percolation threshold of about 6 wt.% can be obtained after heat treatment. Thereby, the production related influence of fibre stretching is largely eliminated.
