During a molding cycle a thermoplastic polymer passes several temperature-dependent aggregate states. Switching to another aggregate state changes the material properties significantly. Because of the molecular structure of amorphous and semicrystalline polymers, different aggregate states and different transition ranges can be determined. The thermal behavior of thermoplastic polymers can be described, illustrated by the time-dependent shear modulus over temperature.
The time-dependent behavior of the shear modulus is illustrated for an amorphous polymer in Fig. 3.22.