Thermoplastics refer to a type of plastic which retains their basic properties -when heated it softens and when cooled it hardens. These plastics can be heated and cooled many times. However, when heated long, it softens and melts to a liquid form. It is reusable as it can be recycled. Polyurethane, acrylics, and Worbla are different types of thermoplastics.
In Art, because of its specific pliable property (when heated it becomes soft), it is molded in desired shapes and sizes for sculptures and in art galleries to make masks, armor, ornaments or its replicas.