What defines thermosetting polymers?

Thermosetting polymers are characterized by the presence of strong covalent bonds that create crosslinks between the polymer chains. This network of crosslinks gives thermosetting polymers their rigidity and stability. Once they are set into a particular shape through the application of heat, these polymers cannot be remolded or reshaped upon reheating. This is in contrast to thermoplastics, which soften when heated and can be reshaped multiple times. The crosslinked structure of thermosetting polymers also contributes to their resistance to deformation and chemical resistance, making them ideal for applications where durability is crucial.

The other options describe properties more characteristic of different types of materials, rather than thermosetting polymers specifically.