Adjective
having the property of becoming permanently hard and rigid when heated or cured
Source: WordNetthe phenol resins and plastics were the original synthetic thermosetting materials Source: Internet
Thermosetting mechanisms, on the other hand, are true curing mechanism that involve chemical reaction(s) among the polymers that make up the binder. citation Thermoplastic mechanisms: Some films are formed by simple cooling of the binder. Source: Internet
Thermosetting resins such as Bakelite required heat and pressure during the molding cycle, but could be removed from the molding process without being cooled, again making the molding process faster. Source: Internet