Photo: Dark red Self-Lube HCR Silicone HV Cable Connector Seal

Self-lubricating (or Self-Bleeding or Oil-Impregnated) silicones are very helpful for seals that require reduced friction for various reasons. Usually, these are hand-inserted seals that need reduced insertion forces (e.g., peripheral seals). Sometimes, it is to reduce the chance of damage during installation (e.g., MAT seals). In some cases, the oil itself is useful for its anti-corrosion properties.

The benefits of self-lube materials over a separate surface lubricant application process are both quality and cost-effectiveness. The slight increase in material cost is typically cheaper overall than the labor cost of adding the lubrication in a separate step. In terms of quality, you can guarantee that all surfaces of a seal are lubricated and will stay lubricated with a self-lube material, whereas a separate process has a higher risk.

Silicone, both HCR (high consistency rubber) and LSR (liquid silicone rubber), is currently the principal material that is commonly used for high-performance applications. This is because VMQ silicone is only slightly resistant to oils, and the silicone actively tries to reject the oil from within, pushing it to the outer surface. However, at low oil content levels (8% and under), the oil doesn't dramatically affect physical performance.

Other HCRs can use this same oil but with more degrading effects. Other lubricants, such as liquid paraffin in EPDM or naphthenic oil in nitrile HCRs, have a higher risk for temperature and compatibility.

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