Originally, insulators were made from materials like ceramic and glass. But in 1963, a new type, made from polymers, was introduced. However, recent improvements in their design and making have made them popular with power companies and utilities. These insulators have a fiberglass core and are covered with protective parts made of rubbery materials such as silicone, polytetrafluoroethylene, or EPDM. They also have metal parts at both ends for connection. Also, known as composite insulators, they combine at least two different insulating materials, a sturdy core and a protective housing with end fittings.
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