Thermosetting refers to a type of polymer that hardens permanently when heated and cannot be remolded or reheated. This process occurs during the curing stage, where the material undergoes a chemical change, forming strong cross-links between the polymer chains. Common examples of thermosetting materials include epoxy, phenolic, and polyurethane. Once set, thermosetting plastics exhibit excellent heat resistance, chemical stability, and durability, making them ideal for various applications. They are often used in electrical insulators, automotive parts, and household items. Unlike thermoplastics, which can be reshaped, thermosetting materials maintain their form and strength under high temperatures.