Complex sentence: Depending on the chemical structure, polyester can be a thermoplastic or thermoset, there are also polyester resins cured by hardeners; however, the most common polyesters are thermoplastics.
Split into simpler sentences: Depending on the chemical structure, polyester can be a thermoplastic or thermoset. There are also polyester resins cured by hardeners; however, the most common polyesters are thermoplastics.