What is a characteristic of thermoset plastics?

Thermoset plastics are characterized by their unique molecular structure, which undergoes a chemical change during the curing process. Once set, thermosets form a rigid structure that is stable and retains its shape even under heat or stress. This means that they cannot be melted down and reshaped as some other types of plastics can.

In contrast, thermoplastics can be reheated and reshaped multiple times, which allows for greater flexibility in manufacturing and design. While thermoset plastics are often noted for their durability and heat resistance, they are not typically classified as low-cost materials. Additionally, food containers are generally made from thermoplastics rather than thermosets, as thermoplastics can provide better safety and regulatory compliance for food use. Thus, the defining trait of thermoset plastics being the inability to be reshaped after curing is the key characteristic that makes this answer correct.