Either thermoplastic or thermosetting polymers may be used. Natural rubber is an elastomer and a thermoplastic. The powder may be a thermoplastic or a thermoset polymer. SMPs include thermoplastic and thermoset (covalently cross-linked) polymeric materials. Polymers with thermoplastic behavior are applicable for melt blowing. Depending on the chemical structure, polyester can be a thermoplastic or thermoset. The bobbin may be made of thermoplastic or thermosetting (for example, phenolic) materials. It used less expensive materials, such as injection-molded thermoplastic instead of carbon fiber. Desmopan or Elastollan are examples of thermoplastic polyurethanes (TPU). Unlike PS-I and SBC, it is not a thermoplastic, but an elastomer. PBT is closely related to other thermoplastic polyesters. Most plastic pipe systems are made from thermoplastic materials. The carbon fibers were loosely woven into a tube along with fibers of thermoplastic. Polyphenylene sulfide is an engineering plastic, commonly used today as a high-performance thermoplastic. Modern paper or film dielectric capacitors are dipped in a hard thermoplastic.