Extruder flat-film draw-ratio

Attempts to extrude 1.0 mm thick films of amorphous PET at draw ratio > 7 failed because of fracture at the edges of the film. All the film extrusions discussed so far involve films that are the same size as the flat surface of the split billet. A 1.0 mm thick film of PET was cut so that it was 1/2 the width of the billet surface and positioned in a groove in the center of the billet (Figure 4). Using this configuration, a coherent film of draw ratio 12 was obtained, nearly double the previous value. 

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