Section insulators of electric traction systems

A section insulator adapted to be inserted directly in a contact wire in an electric traction system having at least one vehicle constrained to move in at least one predetermined path and having a pick-up shoe, and at least one contact wire for supplying electric current to the said shoe comprising an elongate body of synthetic resin, reinforced with glass fibres or other fibres of high tensile strength, the improvement whereby substantially the whole of the exposed surface of said insulator is formed of a composition based on a cycloaliphatic epoxy resin cured with an acidic curing agent and having a running surface for engagement with said shoe that is continuous from end to end over at least a major portion of the length of the body and is formed by a composition comprising the cured reaction product of 100 parts of a cycloaliphatic epoxy resin, 40 - 250 parts of an acidic hardener therefor and an effective amount of an accelerator, and dispersed in the said reaction product 50 - 400 parts of a mineral filler substantially wholly in the form of particles not greater in any dimension than 80 micrometers and 10-100 parts of a low-friction fluorocarbon polymer.