Conductive hybrid polymer composites based on recycled carbon fibres and carbon nanofillers

The aim of this study was to investigate potential applications of milled secondary carbon fibres as a primary filler in conductive polymer composites. The examined composites were based on epoxy resin, milled secondary carbon fibres and selected carbon nanoadditive used as a secondary conductive filler. Three kinds of nanopowders were tested: multiwalled carbon nanotubes, graphene nanoplatelets and graphitized carbon black. In the first stage of the experiment, composites with different percentages of carbon fibres were examined in order to determine the electrical conductivity and percolation threshold. Subsequently, the most conductive composition (70% of carbon fibres, sigma = 9.05 S cm(-1)) was modified by adding nanofillers. The addition of carbon nanotubes caused more than twofold increase in in-plane conductivity to 20.18 S cm(-1). The composites with graphene nanoplatelets showed deterioration of properties due to strongly increased viscosity of a binder with graphene. Small loadings of graphitized carbon black had a minor positive impact on the electrical conductivity and mechanical properties of composites.