FSU researchers created a novel technique to improve the lightweight electromagnetic interference (EMI) shielding properties based on preformed thin films or buckypaper layers made of single-walled carbon nanotube (SWNT), multi-walled carbon nanotube (MWNT), carbon nanofibers (CNF), and their mixed forms in composites. Carbon nanotubes are promising material for EMI shielding because of their electrical conducting properties and lighter weight compared to metal. Film materials made of entangled network using carbon nanotubes, called buckypapers (BP), provides free standing films. The film materials are easy to be use and integrate into various structures and composites fabrication processes to reduce manufacturing cost. Nanotube buckypapers can have an areal density from 18.1 g/m2 to 21.5 g/m2, while offering electrical conductivity as high as 50S/cm to 8,000S/cm.
To improve the EMI shielding effectiveness (SE), layers of BP were stacked together. The absorption loss increased due to the increased thickness of conducting material since the thickness of individual BP layers is usually less than 30 mm. However, in experiments, the EMI SE does not linearly increase with the increased of number of BP layers directly stacked together. Since the absorption contribution to the total SE is small as a result of directly stacking multiple BP layers together, we discovered a new method to effectively utilize internal multiple reflection effects to further improve the SE. This invention achieves high EMI shielding effectiveness by inserting polymer insulators in between conducting nanotube buckypaper layers in composites.
