In-situ observation of electrophoresis of conductive and semi-conductive micro particles in epoxy resin

Electrophoresis phenomena of conductive and semi conductive micro particles in liquid epoxy/anhydride mixture were in-situ observed by optical microscopy. The polymer mold with plate electrodes which provide horizontal electric field was made for the observation. Graphite, copper and titanium dioxide micro particles were studied in this paper. Because of the existence of space charge, micro particles moved together with liquid epoxy towards electrode under DC electric field. The aggregation and alignment of particles were studied and the theoretical analysis was given. The study shows that the viscosity of epoxy decides the flow type and laminar flow is ideal for the formation of alignment structure, indicating that the suitable moment of applying electric field is the key to produce the high temperature curing epoxy with anisotropic properties. This work shows that the radius, density and shape of particles also affect the alignment under electric field.