In what way do thermoplastics differ from thermosetting plastics?

Thermoplastics differ from thermosetting plastics primarily in their ability to be reshaped upon heating. When thermoplastics are heated, they become flexible and can be molded into various shapes. This property allows for their reuse and reforming, making thermoplastics versatile in many applications. In contrast, thermosetting plastics, once cured through a chemical reaction, maintain their shape and structure even when exposed to heat. They do not melt or reshape after their initial setting, which is why they are often chosen for applications requiring rigidity and stability under heat.

The other options presented do not accurately reflect the fundamental characteristics of thermoplastics and thermosetting plastics. For instance, thermosetting plastics are not always flexible; they are usually rigid after curing. Additionally, thermoplastics can be quite durable, and it's not accurate to say they are universally less durable than thermosetting plastics. Thermosetting plastics cannot be melted once set, which distinguishes them from thermoplastics in terms of thermal behavior.