thermosetting

[thur-moh-set-ing] /ˈθɜr moʊˌsɛt ɪŋ/
adjective
1.
pertaining to a type of plastic, as the urea resins, that sets when heated and cannot be remolded.
Origin
1935-40; thermo- + setting
British Dictionary definitions for thermosetting

thermosetting

/ˌθɜːməʊˈsɛtɪŋ/
adjective
1.
(of a material, esp a synthetic plastic or resin) hardening permanently after one application of heat and pressure. Thermosetting plastics, such as phenol-formaldehyde, cannot be remoulded Compare thermoplastic
thermosetting in Science
thermosetting
  (thûr'mō-sět'ĭng)   
Relating to a compound that softens when initially heated, but hardens permanently once it has cooled. Thermosetting materials are made of long-chain polymers that cross-link with each other after they have been heated, rendering the substance permanently hard. Compare thermoplastic.