Thermoforming operation of semi-crystalline polymers with glass transition temperature, $T_{g}$, and melting temperature, $T_{m}$, is carried out at a temperature $T$, in the range of
- $T_{g} < T < T_{m}$
- $T_{g} < T < T_{m}$
- $T_{g}>T=T_{m}$
- $T_{g}>T>T_{m}$
