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Low-Density Rigid Foam for Dielectric Applications Offer Clear Advantages

General Plastics recently introduced its advanced dielectric foam material for use in radomes, antennas and other radio frequency (RF) communication systems. The LAST-A-FOAM® RF-2200 Dielectric Series is a thermoset plastic that addresses diverse needs for an RF-transparent protective layer with extended thermal processing capabilities. These include a low dielectric constant and low-loss properties supported by products in a low density range.

Fulfilling designer needs

The RF-2200 materials offer numerous advantages, ranging from high processing temperatures to their resistance to water absorption. This material was formulated with a glass transition temperature (Tg) that supports usage temperatures up to 350°F. This allows thermal curing of high-temperature composite prepregs and supports manufacturing processes compatible with BMI resins. As a result of these improved thermal/mechanical properties, designers can produce panels with greater dimensional stability, which is essential for reliable, long-lasting performance in the field, even in extreme environments.

Another notable feature of LAST-A-FOAM® materials is that its dielectric performance is unchanged even when exposed to moisture. “Our foam’s chemistry doesn’t break down,” said Technical Sales Manager Joe Nichols. “Rain or moisture on the foam’s surface isn’t absorbed into the foam as can happen with other dielectric materials, dramatically changing their dielectric performance.”

In addition to the material’s ability to resist water uptake, RF-2200 foams are offered in custom sizes. Further, their density and cell shape are consistent from sheet to sheet and within each block. Their homogenous cell structure improves signal transmission and reception.

Far-ranging applications and environments

The RF-2200 series, along with our higher-density dielectric materials (FR-3700 and FR-7100), neither inhibits nor changes transmission of signals. It is primarily used as composite material in construction of radomes, antennas and for electronics isolation. These structures can range in size from the small domes seen on yachts to extremely large coverings spanning dishes that resemble covered stadiums. Since the low-density RF-2200 withstands higher processing temperatures, it supports thermal curing of prepregs used to create stronger, more durable panels. The material is also lightweight, and easy to handle, machine and coat, which makes it ideal for assembling and installing panels in a space-frame radome.

When it comes to the material’s physical properties, we can ensure reliable performance in the field. General Plastics’ dielectric foam has been used as part of the radome structures on naval attack vessels. Because the radomes shield the radar or communications for military access, reliable performance is critical. These defense customers count on the strength, dimensional stability, endurance and water resistance of our dielectric materials.

Other applications include radomes that protect Doppler radar, which is used to measure the direction, speed or velocity of precipitation, and thus, wind.  At airports it helps to determine if it’s safe for airplanes to land. “Doppler radar helps air traffic controllers assess levels of wind shear. This application is for land based radar and radomes,” said Nichols. “The simple radome structures on these antennas hold up to hail and variable high-to-low temperature exposures.”

RF foams as integral antenna components

With the increasing ubiquity of antenna systems for communications and data delivery, our RF-2200 foams are also proving an ideal material for active, internal components of antenna systems.

“We’re seeing our dielectric foams used as stand-offs or other spacer materials in antenna designs,” said Nichols. “Oftentimes the distances between active components are critical to the performance of those antennas. Our materials are potentially transparent to the radio waves, but keep the other components at their proper distance and location so they perform correctly.”

These products are lightweight, yet stable and capable of accommodating the design loads that will be applied to them. So, even in situations of high wind, hail strikes or other potential environmental dangers, the antenna continues to perform over its design life.

As the world moves faster, the desire for continuous data access is driving development of new antenna systems to extend Internet access and communications capabilities on everything from personal vehicles to public transportation. General Plastics is involved in these applications, which require lightweight RF foam materials to support very large antennas moving huge volumes of data.

Electronics isolation applications

Our new polyurethane RF foams are also used for the testing and packaging of electronics. Nichols says that makers of high-end electronics need to test their products at specific stages of manufacturing. “They will request the dielectric properties of our foams because they need materials that will not reflect or absorb radio waves – that’s a critical part of their test apparatus,” he said. “Our RF-2200 materials allow them to support the equipment that’s being tested without interacting with the radio waves themselves.”

Similarly, these materials can be used as electronic packaging insulation and electrical isolators, used appropriately to alter or manage the electrical surroundings of components.

LAST-A-FOAM® RF-2200 is offered in densities of 3, 4 and 6 pounds per cubic foot. General Plastics offers custom densities to satisfy project requirements for a specific dielectric constant and/or loss tangent. Beyond providing material and relevant technical expertise, we can also support customers’ needs for machined-to-spec, ready-for-assembly parts.

“Our team of expert engineers and chemists is always eager to determine the properties a customer needs and offer them the most value-appropriate product,” Nichols said.