6. Conclusion

The film blowing process produces very large, thin films (a few tens of micrometers) from relatively compact tooling. The films produced are partially bi-oriented, with more homogeneous mechanical properties than films produced by flat extrusion. Recent technological advances have focused on improving extrusion line control and monitoring. Internal cooling systems and modular cooling rings reduce variability (thickness and width) while increasing productivity. With the advent of stackable dies, film producers have gained in flexibility and new structures.

Modeling helps us understand :

• flows occurring in the different types of die ;

• rheological behavior of polymers and their thermodependence ;

• the behavior of polymers when stretched in air;...