FST to Kick Off Production of New Seals in Spring

Freudenberg Sealing Technologies (FST) has recently unveiled a new high-performance material that ensures shock absorbers perform well in extremely low temperatures, down to -40˚F. Slated to come into use in damper seals for cars and commercial vehicles, the new material mixture is more wear-resistant than standard materials. The company reveals that the first series production of the seals will begin in the spring of this year.

When a rubber component is cooled, it loses its elastic characteristics at a specific temperature. Beneath this threshold, it becomes as hard as glass—which is why engineers talk about the “glass transition point”. Nowadays, fluoro rubber mixtures are used in the seals integrated into a number of shock absorbers. These materials become extremely brittle at nearly -4˚F. Though the dampers sustain their leak tightness at lower temperatures, they are prone to damage, particularly when high lateral load are applied to the damper—for instance, when a car runs over a high curb. The seal carries out a critical task in the shock absorber: it seals the oil-filled working space where the valve piston moves back and forth. This transforms the mechanical energy, which is presented when the car travels over an uneven surface, into heat and guarantees that it keeps its four wheels on the road. Hence, it is clear that driving safety is put to risk when there is an oil leak.

The sealing of monotube shock absorbers, which are mainly used in sports cars and in the thriving sports utility vehicle (SUV) segment, is particularly demanding. In this design, the oil is placed under pressure by a gas. An extra damper seal separates the two media from one another. The pressures exerted on the seal can reach 100 bar or more.

Cross-linked with peroxides, special low temperature polymers are used to extend the temperature range where fluoro rubber can be used. However, elastomers produced in this way typically show increased wear.

In a statement, Randolph Gaa, materials expert at FST, explained that this is due to the chemical structure at the points where the molecules are bonded with one another during vulcanization. The basic research of the company found a way to meld incompatible material characteristics with one another. Moreover, the frictional characteristics of the new material barely fluctuate over the temperature sequence. This is crucial since drivers anticipate reproducible and therefore, identical driving behavior in every situation.

The first-ever high-volume application of the new technology is about to happen. In fact, a European carmaker is now utilizing seals made of the new material mixture from FST on an ongoing basis, which is being used in monotube shock absorbers for SUVs.

According to Jürgen Emig, head of product development for shock absorber seals at the company, vehicles of these types are in use around the world and have to prove themselves in both Siberia and the desert. He noted that since the increased low-temperature resistance is solely because of the enhanced material characteristics, the shock absorber does not require design changes. Thus, this enables conversion of existing vehicle models to the new seals retroactively.

The new sealing materials are also applicable for shock absorbers in commercial vehicles. With current materials, commercial vehicle damping seals are reinforced with a steering to meet this requirement. If the all-new, reduced-wear material from FST is used, the design could be changed. For this reason, a damper seal which is now being tested, has only one spring to guarantee complete leak tightness. It is anticipated to go into series production next year.

Just like all chassis components in today’s cars, future generations of shock absorbers should become lighter. This is why FST is looking into the integration of plastics as a carrier part for damper seals, which would replace some of the presently integrated aluminum or steel components. Among other options, the piston, which includes the seal, could be soon be produced with the two-component injection molding process.

Emig concludes that in the event it is successful, it is possible to have weight savings of 30 to 50 percent.