Technology: Freudenberg develops new EPDM for aerospace seals

Plymouth, Michigan – Freudenberg Sealing Technologies (FST) has begun manufacturing seals made from a new EPDM material, which is claimed to address hydraulic seal leakage at high altitudes and low temperatures. 

The new 80 EPDM 426288, with a “breakthrough formulation”, enables seals hydraulic systems to operate at temperatures as low as -85°F (-65°C), said FST in a 6 July statement. 

To produce the material, scientists at FST used a “unique polymer”, rather than adding large amounts of plasticisers, the statement added. 

The EPDM material, according to FST, meets the rigorous requirements of the new AMS7361 specification for improved low temperature behaviour in commercial aircraft hydraulic systems. 

In both lab testing and application, it demonstrated “superior, low-temperature, sealing behaviour after extensive exposure to fluids, pressures and temperature extremes,” the company added. 

The rubber can also be crafted to resist sunlight, ozone and chemical degradation, effectively sealing phosphate-ester hydraulic fluids and other fluids and performing well at temperatures of up to 302°F (150°C).

According to FST, commercial airliners – which cruise at altitudes of up to 42,000 feet (12,801 m) and 575 mph (926 km/h) – rely on standard EPDM to seal critical hydraulic systems such as landing gears. 

At such altitudes and speeds, frictional heat maintains hydraulic system temperatures within a range that preserves the performance integrity of traditional EPDM components. 

However, turboprop transport carriers and unmanned aerial vehicles, or drones, fly at much slower speeds but at the same altitude.

This reduces air friction and heat on aircraft’s exterior, meaning that the aircraft must endure extended periods of very cold temperatures, followed by an abrupt change in temperature when they land. 

Standard EPDMs cannot tolerate prolonged exposure to very low temperatures without becoming brittle and cracking. 

To address the issue, FST’s materials research fellow Dr Paul Hochgesang, based in the company’s Plymouth central laboratories, initially developed several new EPDM formulas, using more advanced monomer and polymer technology.

While the formulas showed "excellent results" in meeting the material standards required in the aerospace industry, they still could not pass prolonged cold testing without losing strength and becoming brittle, FST said.. 

“We blended a variety of ingredients, including plasticisers, fillers and heat stabilisers, and still could not achieve the temperature gradient our customers needed,” Hochgesang said. “That’s when the company’s material and sourcing experts in Germany and Japan stepped in to help.

Hochgesang was introduced to a new, largely unknown industrial polymer, said FST without giving further information about the polymer. 

“When added to a new EPDM formulation, the resulting material not only met, but exceeded, the cold temperature requirements needed by aerospace customers,” the company added. 

According to FST, seals and components made from the EPDM materials have already been manufactured and tested in North America and Europe by several “major aerospace manufacturers and system suppliers.” 

“Based on extremely positive customer feedback and reports, production of aerospace O-rings made from this new EPDM has been launched,” it added.