A resin material is provided which comprises at least one thermoset resin, carbon conductive additive material, and at least one thermoplastic polymer resin. The thermoplastic polymer resin dissolves in the thermoset polymer resin and phase separates upon cure. There is also provided a method of making the resin material, and additionally a composite material that comprising said resin material in combination with a fibrous reinforcement. The resin material and composite material may each be used in an uncured or cured form, and may find particular use as a prepreg material.