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Precision Polymer Engineering has launched a range of lead-free FKM grades that comply with Reach legislation.

The company’s lead-free, steam-resistant fluoroelastomer, V75J, has been developed to provide improved in-service performance over lead-cured seals in high-performance sealing applications.

Traditionally, lead oxide was used in the litharge curing process during seal manufacture to increase steam resistance of fluorocarbon elastomers.

Materials experts at PPE have improved the strength of a peroxide-cured, terpolymer, FKM using filler combinations.

The result, V75J, is one of a number of fluoroelastomers from PPE that display outstanding resistance to hot water and steam without the use of litharge curatives.

These materials also offer resistance to oils, fuels and hydraulic fluids, high-temperature performance and long-term sealing ability.

Fluoroelastomers have two main cure profiles: bisphenol cure and peroxide cure.

Although peroxide-cured materials have a better inherent steam resistance than bisphenol cured alternatives, they tend to be weaker.

Bisphenol-cured elastomers are typically formulated with metallic oxides, of which lead oxide (litharge) is the traditional choice for steam resistant applications because it prevents the seal from swelling when it comes into contact with water or steam.

In recent independent fluid immersion tests, V75J was benchmarked against 11 leading material compounds (including perfluoroelastomers) in water/steam for 1,000 hours at 140C.

V75J was found to be the best performing material followed by Perlasta G80A.

The remaining materials were badly deformed or disintegrated.

In another example, V75J was chosen by an engine manufacturer to replace an incumbent litharge-cured FKM.

The existing material was failing prematurely due to excessive temperatures causing ‘un-crosslinking’, leading to failures within the warranty period of the engine.

By replacing this material with V75J, the customer significantly extended the life of the seals beyond the warranty period.

Precision Polymer Engineering

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