ABSTRACT:The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers. The resulting composites can be used in applications such as electrostatic dissipation and interference shielding. Electrical conductivity models are often proposed to predict the conductivity behavior of these materials. The electrical conductivity of carbon-filled polymers was studied here by the addition of three single fillers to nylon 6,6 and polycarbonate in increasing concentrations. The fillers used in this project were carbon black, synthetic-graphite particles, and milled pitch-based carbon fibers. Materials were extruded and injection-molded into test specimens, and then the electrical conductivity was measured. Additional material characterization tests included optical microscopy for determining the filler aspect ratio and orientation. The filler and matrix surface energies were also determined. An updated model developed by Mamunya and others and a new additive model (including the constituent conductivities, filler volume fraction, percolation threshold, constituent surface energies, filler aspect ratio, and filler orientation) fit the electrical conductivity results well.

The electrical conductivity of polymeric materials can be increased by the addition of carbon fillers, such as carbon fibers, carbon black, and synthetic graphite. The resulting composites could be used in applications such as electromagnetic and radio frequency interference shielding and electrostatic dissipation. A significant amount of work has been conducted varying the amount of single conductive fillers in a composite material. In contrast, very limited work has been conducted concerning the effect of combinations of various types of conductive fillers. In this study, three different carbon fillers were used: carbon black, synthetic graphite pareticles, and pitch based carbon fiber. Two different polymers were used: nylon 6,6 and polycarbonate. The goal of this project was to determine the effect of each filler and combinations of different fillers on the electrical conductivity of conductive resins. A 23 factorial design was analyzed to determine the effects of the three different carbon fillers in nylon 6,6 and polycarbonate. The results showed that carbon black caused the largest increase in composite electrical conductivity. The factorial design analysis also showed that combinations of different carbon fillers do have a positive synergistic effect, thereby increasing the composite electrical conductivity.

Michigan Technological Unwersity Howhton, Michigan 49931 -1 295Increasing 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 adding various carbon based conductive fillers and a chopped glass fiber to nylon 6.6. These materials were extruded and injection molded into test specimens. Tensile tests as well as in-plane electrical resistivity, in-plane thermal conductivity, and through-plane thermal conductivity tests were conducted. One successful formulation consisted of 1Wh 3.2 mm chopped E-glass fiber/ 15Oh Thermocarb (high quality synthetic powdered graphite)/5Yo carbon black/70% nylon 6,6 (all Yo in wt%). For this formulation, the in-plane electrical resistivity was reduced from 1015 ohm-cm (neat nylon 6,6) to 15 ohm-cm. The through-plane thermal conductivity increased from 0.25 W/mK (neat nylon 6.6) to 0.7 W/mK. The tensile elongation at failure was 1.4%.

ABSTRACT:Increasing the thermal conductivity of typically insulating polymers, such as nylon 6,6, opens new markets. A thermally conductive resin can be used for heatsink applications. This research focused on performing compounding runs followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 2 3 factorial design and a complete replicate in each polymer. The objective of this article was to determine the effects and interactions of each filler on the thermal conductivity properties of the conductive resins. From the through-plane thermal conductivity results, it was determined that for both nylon 6,6 and polycarbonate based resins, synthetic graphite particles caused the largest increase in composite thermal conductivity, followed by carbon fibers. The combination of synthetic graphite particles and carbon fiber had the third most important effect on composite thermal conductivity.

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, 200p 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 24 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.

ABSTRACT:Increasing the thermal conductivity of typically insulating polymers opens new markets. A thermally conductive resin can be used for heat-sink applications. This research focused on extruding followed by injection molding and thermal conductivity testing of carbon filled nylon 6,6 and polycarbonate-based resins. The three carbon fillers investigated included an electrically conductive carbon black, synthetic graphite particles, and a milled pitch-based carbon fiber. For each polymer, conductive resins were produced and tested that contained varying amounts of these single carbon fillers. In addition, combinations of fillers were investigated by conducting a full 2 3 factorial design and a complete replicate in each polymer. These through-plane thermal conductivity experimental results were then compared to results predicted by several different thermal conductivity models. An improved thermal conductivity model was developed that fit the experimental results well for resins that contained single fillers and combinations of different fillers. This improved model was based on the original Nielsen model. A single value for the shape parameter, A (which is needed in Nielsen's model), was used for all three different fillers.

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Increasing the thermal and electrical conductivity of typically insulating polymers, such as nylons, would open new markets. A thermally conductive resin could be used for heat sink applications. An electrically conductive resin could be used in static dissipative and Electromagnetic Interference/Radio Frequency Interference shielding applications. This research focused on adding conductive fillers (namely carbon black and Thermocarb, a high quality synthetic milled graphite) and a chopped glass fiber to high temperature nylon. These materials were extruded and injection molded into test specimens. Tensile tests as well as in-plane electrical resistivity, in-plane thermal conductivity, and through-plane thermal conductivity tests were conducted.