(738e) Optimization of a Benign Supercritical Carbon Dioxide Treatment for Carbon Nanotube Nanocomposites

In this work, a benign method of deagglomerating commercially available carbon nanotubes (CNT) using supercritical carbon dioxide (scCO₂) was optimized. Twin screw extrusion is the current method employed to disperse and reduce these agglomerates in polymer matricies, but results in significant destruction of the CNT in applications where aspect ratio retention is desired (up to 70% decrease in length). Thermodynamic principles were employed to discover that the optimal soak temperatures and pressures corresponded to a scCO₂ fluid density of ~750 kg/m­­³ for the current apparatus. Soak time and CNT/scCO₂ ratio were also studied to acquire a more comprehensive understanding of the system. Transmission electron microscopy was utilized to determine the nanotube lengths both before and after scCO₂ treatment of Baytube C150 P and Nanocyl NC-7000. The best case expansions resulted in a decrease in CNT bulk density from 150 kg/m³ (Baytube) and 50 kg/m³ Nanocyl) to 5 kg/m³ and 1 kg/m³ respectively. It was discovered that the scCO₂treatment did not damage the nanotubes. Inclusion of the CNT into polymer may result in improved conductivity, mechanical properties, and reduced percolation threshold.

Acknowledgments: The authors would like to thank Bayer MaterialScience for funding this research. Also thanks to Dr. Erdogan Kiran for thoughtful advice in designing the experiments for pressure and temperature optimization.