AFRL Scientists Identify Method for Applying EMI Shielding Materials Published Dec. 28, 2006 By HQ AFRL HQ AFRL WRIGHT-PATTERSON AIR FORCE BASE, Ohio -- AFRL scientists discovered a suitable method for applying a polymer nanocomposite solution to serve as electromagnetic interference (EMI) shielding material. These materials protect ground-based structures, aircraft, spacecraft, and satellites from internal and external EMI effects. Replacing conventional aluminum systems with polymer nanocomposites for EMI shielding will reduce weight and eliminate corrosion that originates in hardware needed to keep the aluminum in place. The new method is also well suited as a retrofit technology, since it is quickly and easily adaptable to systems that are currently unshielded. Many current systems rely on EMI shielding techniques involving the addition of aluminum foils to the composite structure. Such techniques require that the foils be glued parasitically to each individual panel before assembly. They also require the use of conductive grounding straps with fasteners to achieve a complete enclosure. Consequently, these existing methods add unnecessary weight, increase manufacturing time, and initiate galvanic corrosion, a problem that occurs when bolts are used to connect structural elements with dissimilar electrochemical properties.AFRL's development of a polymer nanocomposite material that can be integrated directly onto structures eliminates the need for such problematic fasteners, at the same time decreasing the amount of excess weight associated with aluminum systems. The research team also improved the mixing techniques needed for preserving adequate dispersion of particles throughout the application process. The newly developed method uses the Thinky® planetary mixer (model ARE 250) to disperse the nanofibers evenly without damaging them. In addition, the researchers devised a method for spraying the mixed solution directly onto the structure; their approach uses a setup very similar to that of an automotive paint sprayer. Provided the solution is mixed to the proper viscosity and concentration, this direct application method not only provides an even coating but also preserves the uniform mixture of the nanoparticles required for sufficient shielding.