3. Parameters affecting bubble geometry

The main difference between sheath blow molding and most other polymer processing methods is the presence of a free surface several meters long. In tube blow molding, the presence of a free surface results in a multitude of bubble profiles. The parameters controlling bubble geometry need to be well understood in order to produce a stable bubble with the desired dimensions and properties. Bubble geometry is controlled by :

• drawing conditions (BUR and Dr);

• cooling rate ;

• the thermal and rheological properties of the materials used.

Figure