Factorial design approach applied to electrically and thermally conductive nylon 6,6

Abstract

Increasing the thermal and electrical conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heat sink applications. An electrically conductive resin can be used in static dissipative and Electromagnetic Interference/Radio Frequency Interference shielding applications. This research focused on performing compounding runs followed by injection molding and testing (tensile properties, volumetric electrical resistivity, and through-plane thermal conductivity) of carbon filled nylon 6,6. The four carbon fillers investigated included a PAN-based carbon fiber (milled, 200μ long), an electrically conductive carbon black, vapor grown graphitic nanotubes, and Thermocarb (high quality synthetic milled graphite). Formulations were produced and tested that contained varying amounts of a single carbon filler. Combinations of fillers were also investigated via conducting half of a 2 4 factorial design. It was determined that Thermocarb has the largest effect on the thermal conductivity. Increasing Thermocarb increases thermal conductivity. For conductive resins containing only a single filler type, nanotubes caused the electrical resistivity (ER) to decrease the most. For the half fraction factorial design formulations that contain at least one filler type at the higher level, the ER of the conductive resin ranged from 0.1 to 0.3 ohm-cm.