Innovative performance material for advanced sealing technology

Paul Boughton

Isolast is a perfluoroelastomer, developed to meet the needs of companies requiring sealing materials with the elasticity of a conventional elastomer, but with the chemical resistance of PTFE (polytetrafluoroeten) and able to cope with uninterrupted use at temperatures of as much as 325˚C. Isolast formulas are developed internally in collaboration with polymer suppliers, and Isolast is manufactured and moulded in-house.

Developers at Trelleborg provide customised design solutions using the innovative Isolast perfluoroelastomer, which has proved a winner in independent industry tests.

"We've been developing Isolast for the past 10 years and now have a variety of materials in our portfolio to suit a wide range of demanding applications," explains Chris Stowell, technical manager. "This is a technically advanced, high performance material for situations involving extreme temperatures or aggressive process chemicals."

Although Isolast was originally used in mechanical seals for refinery applications and in pumps and valves for large-scale chemical production, Trelleborg Sealing Solutions has since become established in a wide range of industries including the aerospace and pharmaceutical sectors.

"Isolast is now used in aircraft engines, where temperatures exceed the performance characteristics of raditional fluoroelastomers," explains Stowell. "Replacing these with Isolast increased average overhaul intervals," he adds. "Isolast is also used by a major pharmaceutical manufacturer for its vaccine-production process."

"Not only do all of its materials have to be internationally approved, but they need an extended life," explains Stowell "'In this kind of application, conventional elastomers have a short and unpredictable lifespan. Any failure in the sealing element is very expensive and batches must be rejected," he says. Isolast's long-term performance under demanding conditions is crucial for companies like this."

Designing customised industrial solutions is the way forward. One recent solution involved a safety-relief valve in a refrigeration application.

The customer had a three piece valve arrangement with two brass components and a conventional elastomeric seal between them," says Stowell. "There were also 14 different types of elastomer which could be specified for the valve, depending on the refrigerant or lubricant used, which was causing all kinds of problems," he adds.

The seal was quite large and replacing it with Isolast would have been very expensive, so we decided to redesign the whole valve, turning it into a one-piece unit with a much smaller amount of Isolast bonded into it.

"The customer was delighted," says Stowell. "We've since supplied almost 40 000 parts to them and in four years, the customer hasn't had a single reject from its clients," he says. "Isolast is at the extreme edge of the elastomer spectrum and allows us to do things with seals that wouldn' be possible with conventional elastomers," says Stowell. "By pursuing this innovation, we will find new and efficient ways of solving our customers' problems."

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