Tension, stress and friction?

›› OVE 40 SL – Conductivity for seals

The new functional conductive coating counteracts static charging of elastomer seals
How should the conductivity of OVE40SL be assessed?

A good seal should be tight, flexible and resistant. Elastomers fit perfectly into the picture here.
But with all the advantages that elastomers bring with them, there are also two undesirable phenomena. In addition to high coefficients of friction, many elastomers tend to become electrostatically charged. Previous remedial measures are expensive or unsuitable for sealing elements. Our new coating solution now makes seals conductive and makes them easier to handle.

Static charging of components can lead to unpleasant and harmful effects. With some materials, negative effects become apparent very early. Already after production, when seals are packed, they stick to each other or to the bags due to the static charging. Finally unpacked, they immediately attract dust and other dirt, making them unsuitable for cleanliness-critical applications. Separation is also difficult and disruptive in assembly plants. Downtime and long throughput times are the result. In individual cases, the charges on the components can even build up and disrupt or damage sensitive electronic peripheral components.

By default, elastomers are not or only slightly conductive or dissipative. The aim of all measures is to minimize static electricity. Various options promise more or less success. What works with metals and other conductors quickly finds its limits with elastomer seals. In order to safely remove static charge from non-conductive components, it is first necessary to make them conductive. Special sealing materials offer one possibility. For seals, which in terms of cost belong to the classic C-parts, the new development of a conductive elastomer material is usually only worthwhile if very large quantities are produced. It is therefore a convenient alternative to only modify the sealing surfaces if necessary. Our newly developed, water-based anti-friction coating optimizes the electrical conductivity of the seals and also ensures low coefficients of friction and easy assembly.

OVE40SL is a water-based and heat-resistant bonded coating modified with special high-performance additives.
It is sprayed onto the seals in a layer thickness of 3-12 μm according to our OVE standard and forms a highly stable surface after curing. The additives ensure good conductivity of the component surfaces and therefor the dissipation of electrostatic charges. At the same time, the elastic yet extremely wear-resistant coating reduces the friction values of the seals. With a resistance range of only 103 Ω ohms, measured according to DIN EN 62631, the coated elastomers are on the level of special materials. For comparison: depending on the filler, standard elastomers can have a resistance of up to 1014Ω ohms.

OVE40SL also achieves dream values with regard to friction and assembly forces. The friction coefficients of the new coating are another 18 percent better than previous records. The measured press-in forces were even 80 percent lower. In addition OVE40SL is far more wear-resistant than comparable coatings. The low friction coefficients achieved remained constantly low for longer times in endurance tests. With bonded coatings that have been common up to now, the coefficients of friction usually increase steadily until the layer is destroyed. All challenges arising from electrostatic charging can be counteracted subsequently with OVE40SL, and that starting from quantities of just 1 piece using manual coating.

Overview coating Products and services
Technical guidance document, version of 31.05.2022

Comparison of OVE coatings

Friction force in % compared to uncoated base ring
Friction force reduction:
Our OVE08T coating achieves the highest friction reduction measured. The values are compared to a cleaned and uncoated base ring and show a cross-section of the base materials EPDM, NBR, FKM (except VMQ).

Insert force in % compared to uncoated base ring
Insert-force reduction:
Our OVE95T coating achieves the highest insert-force reduction measured. The values are compared to a cleaned and uncoated base ring and show a cross-section of the base materials EPDM, NBR, FKM (except VMQ).

Increase of frictional force under contineous motion in %
Increase of frictional force in continuous movement:
Our OVE08T coating has the best long term lubrication properties for use in slightly dynamic applications. The values result from 50 test cycles and show the change of friction force in %.

Physical wear-down of coating (coating adhesion under abrasion) in %
Our OVE40SL coating has excellent abrasive strength (coating resistance):
For this purpose, the rings were subjected to an insertation test until there was no coating on the ring anymore. The compression-set was 25%, which corresponds to a standard application. For rings coated with OVE40SL, the tests were stopped after 50 cycles because there was no change observed.