2. Basics of relevant thermomechanical modeling

Thermoplastic transformation processes are essentially thermomechanical. They comprise three stages (figure 1 ):

• melting, i.e. the transition from a solid, powdered or granulated state to a sufficiently homogeneous, fluid, molten state. The term "melting" covers several different physical phenomena, depending on whether the polymer is semi-crystalline or amorphous;

• shaping in the molten state, by flowing under pressure through a die or into a mould;

• shaping and cooling, possibly including stretching, bi-stretching, blowing operations...

The properties of the object produced depend, of course, on the polymer chosen, but also on the "thermomechanical path"...