3. Implementation

3.1 General

Thermoplastic polyesters are often injection-molded. Some applications call for extrusion.

Injection molding machines need to be able to develop high injection pressures (1,000 to 2,000 bar, or 100 to 200 MPa) to achieve sufficient injection speed to fill the mold before cooling causes the polymer to crystallize.

In addition, the low viscosity of molten polymers requires sufficient clamping force to prevent them from leaking through the parting line.

The screw profile must be adapted to semi-crystalline materials.

A shutter, preferably hydraulically operated, to prevent the molten polymer from flowing to the nozzle, is generally required. The molds must be heatable up to temperatures...