Drying of Aerogels with Supercritical Carbon Dioxide

Significance of the Topic

The use of supercritical CO2 to infuse additives into polyimide films addresses the polymer’s inherent resistance to solvent-based treatments. This approach broadens polyimide applications in aerospace, electronics, and high-reflectivity coatings.

Objectives and Study Overview

This study aims to establish a rapid, eco-friendly method for embedding a silver-based compound into polyimide films using supercritical CO2, producing flexible reflective films without toxic solvents.

Methodology and Instrumentation

The infusion process steps:

• Placement of cured BTDA-ODA polyimide films and 10 wt% COD-AgF6acac additive into a 10 mL high-pressure vessel.
• Pressurization with CO2 to 5000 psi and heating to 110 °C to reach a supercritical state.
• 120 min of additive infusion, followed by cooling, depressurization, film retrieval, and post-curing at 300 °C.

Instrumentation Used:

• Applied Separations’ Spe-ed™ SFE-2 or Helix supercritical fluid system.

Main Results and Discussion

SEM and TEM analyses demonstrated uniform silver distribution and surface coverage. Optical measurements confirmed high reflectivity. The supercritical CO2 process achieved deeper penetration and faster processing compared to traditional liquid solvents.

Practical Benefits and Applications

• Elimination of toxic solvents and associated waste.
• Reduced processing time with a single-step infusion.
• Retention of film flexibility and improved optical properties.
• Recyclability of CO2 for large-scale operations.

Future Trends and Applications

Expanding supercritical CO2 infusion to other metal additives and polymers could enable advanced flexible electronics, electromagnetic shielding, and novel coating solutions. Development of continuous processing and multi-component infusions may enhance industrial adoption.

Conclusion

The supercritical CO2-assisted silver infusion offers an effective, sustainable alternative to conventional solvent methods, yielding reflective, flexible polyimide films with minimal environmental impact.

References

• Boggess, R.; Taylor, L. Infusion of Silver into Polyimides by the use of Supercritical Carbon Dioxide. J. Appl. Polym. Sci. 1997, 64, 1309.
• Nazem, N.; Taylor, L.; Rubira, A. Supercritical Fluid Infusion of A Silver-Containing Compound into Poly(Ether Ether Ketone) for the Purpose of Making Reflective Films.