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 the low-density range.
Fulfilling designer needs
The RF-2200 materials offer numerous advantages, including high processing temperatures and 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 their 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 its ability to resist water uptake, RF-2200 low-dielectric foam is available 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 alters signal transmission. It is primarily used as a composite material in radomes and antennas, and for electronic isolation. These structures can range in size from the small domes seen on yachts to extremely large coverings that span dishes resembling covered stadiums. Since the RF-2200 low-density dielectric foam withstands higher processing temperatures, it enables thermal curing of prepregs, resulting in 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.
Regarding the material’s physical properties, we can ensure reliable performance in the field. General Plastics’ low-dielectric foam has been used in the radome structures of naval attack vessels. Because the radomes shield the radar or communications for military access, reliable performance is critical. These defense customers rely on the strength, dimensional stability, endurance, and water resistance of our low-dielectric foam 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 to be an ideal material for the 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 applied to them. So, even in situations of high winds, hail strikes, or other potential environmental hazards, the antenna continues to perform throughout its design life.
As the world moves faster, the need for continuous data access is driving the development of new antenna systems to extend Internet access and communication capabilities across 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, when appropriate, to alter or manage the electrical environment 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.
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