Evaluation of Non-Carbon Black Based Electrically Conductive Agents for Polyurethane Elastomers

Polyurethane elastomers can have broad applications where electrical conductivity at least at the static dissipative range is desired. In this study, three non-carbon black based additives are evaluated for their performance as conductive agents in a TDI based polyurethane thermosetting elastomer matrix. For this purpose, an ideal additive would provide a volume resistivity less than 1E8 ohm-cm, while having negligible effects on the polyurethane system's physical properties and processing parameters. The criteria for physical properties evaluation included volume resistivity and mechanical properties (shore hardness, tensile, tear, compression set). In addition, chemical leaching of the additive was studied via NIR spectroscopy. Processing parameter evaluation criteria included the reaction profile, where the rate of cure is measured via viscosity buildup. Also, prepolymer blend chemical stability and heat history sensitivity was studied to further understand any processing changes such as storage life and condition. This was done by monitoring the prepolymer/additive blend for up to 48 hours at 70C for viscosity changes and settling behavior and then proceeding to make polyurethane test specimens for the physical properties evaluation. The results show that no one agent was most superior in every criteria. The volume resistivity of the polyurethane was brought down to the 5E6 to 2E7 ohm-cm range. The physical properties of the polyurethane were maintained and the processing parameters were similar and no leaching of additive was detected. To achieve these results, less than 5% loading of conductive agent was required. Based on the evaluation of the accumulated data for all three conductive agents, one was chosen as superior.