Carbon black nanoparticle alignment using magnetic particles creating local percolation spots for electrical conductivity in structural adhesives

Abstract

Due to the rise of structural multi-material concepts in automotive and aerospace industries the role of adhesive bonding is becoming more important in the joining process. In contrast to joining technologies like welding or riveting, an electrical separation of the material by an insulating adhesive layer is given. This might be a problem if humans or electronic devices need to be protected against static discharge. This study investigates the effect of the alignment of non-magnetic spherical carbon black particles by magnetic forces enabled by adding secondary magnetic-sensitive fillers. To achieve this, an epoxy resin filled with carbon black and a small concentration of metal-based particles is used. The metal-based particles are aligned by magnetic forces provided by an external source. During the migration of the metal particles through the viscous epoxy adhesive, the carbon black particles are attached by adhesive forces. It is shown that this effect provides the alignment of non-magnetic carbon black particles, which results in an increased conductivity in carbon black filled epoxy resins.