Which materials are commonly used for outdoor insulators today?

• A. Metal, wood, and composite with steel core.
• B. Porcelain (ceramic), glass, and polymer/composite insulators with a polymer housing around a fiberglass core.
• C. Paper, clay, and epoxy.
• D. Silicon carbide, asbestos, and stone.

Answer: (B)

Outdoor insulators must resist weathering, pollution, UV exposure, and mechanical stress while staying highly non-conductive. Porcelain (ceramic) and glass have long been used because they are hard, electrically insulating, and robust in many outdoor conditions. Modern practice also favors polymer/composite insulators, which use a polymer housing—often silicone rubber—around a fiberglass core. The polymer outer layer provides a hydrophobic surface that helps water bead and break up leakage paths in damp or polluted environments, while the fiberglass core supplies the needed mechanical strength. This combination gives good insulation, lighter weight, and easier handling for outdoor lines. Other materials—metal (which conducts), wood (which degrades), or paper/clay/epoxy mixes, or asbestos-containing materials—are not suitable for durable outdoor insulation.