https://doi.org/10.1351/goldbook.12794
Polymer in the amorphous state above its glass-transition temperature.
Notes:
- A polymer melt has the physical properties of a viscoelastic liquid.
- The term applies both to crystallisable polymers and to polymers that are unable to crystallise. In the latter case, no specifications are needed. In the former case, in the range between the glass-transition temperature and the equilibrium melting temperature, the polymer melt is metastable, and, as long as crystallisation does not occur (see Note 3), the term supercooled polymer melt can be used to define more accurately the thermodynamic state of the system.
- When a crystallisable polymer undergoes crystallisation, the remaining amorphous component cannot be considered a polymer melt. Flow is inhibited by polymer crystallites, which physically cross-link the amorphous component or constrain it at the surface of polymer crystals.