What type of plastic can only be heated and remolded once?

The correct answer is thermoset, which refers to a type of plastic that upon heating and curing, undergoes a chemical change that sets it into a permanent shape. This means that once it is molded and set, it cannot be remelted or reshaped. Thermoset plastics are characterized by their strong, cross-linked molecular structure, which gives them excellent durability and heat resistance, making them suitable for applications where thermal stability is essential, such as in electrical insulations and automotive parts.

In contrast, thermoplastics can be heated multiple times and reshaped without undergoing any chemical change. This allows for greater versatility and reuse in various manufacturing processes. Composites involve a combination of materials, typically consisting of a matrix (which can be thermoset or thermoplastic) and reinforcing fibers, and they can be designed for specific applications. Elastomers are another category that provides flexibility and resilience, allowing for repeated stretching and deformation. Thus, thermoset plastics stand out because of their inability to be remolded after the initial setting.