1) Thermoset 
thermosetting plastic. Compare with thermoplastic. A polymer that solidifies on heating and cannot be remelted. The setting action results from crosslinking of the polymer chains at high temperature- a process that is not reversed by cooling and reheating.
Said of plastics which harden when their polymer chains reticulate in response to heat, radiation and/or a reagent. The chemical bonds thus formed make the material insoluble, more rigid and more temperature-resistant. After reticulation, thermosetting polymers cannot be softened or mechanically recycled without first being broken down
[adj] - having the property of becoming permanently hard and rigid when heated or cured
thermoset, thermosetting 1. A classification for materials that become hardened or cured by the application of heat; such as, acrylic resin. 2. A description of a group of polymers which soften when initially heated, then harden and condense in bulk and retain a permanent shape. They cannot be softened or reprocessed by reheating.
thermoset adjective having the property of becoming permanently hard and rigid when heated or cured; `the phenol resins and plastics were the original synthetic thermosetting materials`
A plastic material that can be softened and molded but cannot be re-used or reverted to its original state.