I'm currently investigate the physical problem of co-extruded blown film (3 layer with ratio 1:5:1) such as melt fracture, gel, skin shark and even inconsistent of thickness.

One of the root cause concern is on the density variation of each layer. Currently the problematic film extruded at following density:

Inner layer density (g/cm^3): 0.91

Middle layer density (g/cm^3): 0.93

Outer layer density (g/cm^3): 0.91

Or do this problem has any critical factor I need to consider?