Hydrophobicity is the main performance of all kinds of insulator. Typically, composite line insulators have smaller average diameters than porcelain or glass insulators.

As a result, an improved flashover performance is achieved by the shape and by the non-wettability of the surface. Wettability characterises the spreading of water on surfaces, and it can be divided in principle into hydrophilic and hydrophobic.
The service experience has shown that the property “hydrophobicity” is vital for a reliable operation under polluted conditions without precautionary maintenance measures such as cleaning or greasing.

Comparing Silicone Rubber with other polymeric materials as well as glass/porcelain as reference, the following principle matrix can be drawn.

Recovery is a well-documented process of Silicone Rubber and means that hydrophobic properties return mainly by reorientation of the methyl groups on the surface of the bulk material.

Transfer is the migration of low molecular chain molecules into the pollution layer from the bulk material. In sufficient amounts, the pollution layer becomes hydrophobic and behaves ideally like an insulator without pollution.

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