Morphology Development in Blown Film

Several morphologies have been described for immiscible blends in blown film, including elongated particles such as fibrils and ribbons. Forming elongated morphologies is a two-step process: 

• Sphere-like dispersed domains are formed during extrusion (in the absence of blowing or drawing). Shear flow fields in the extruder and die dominate the morphology. The domain size is a function of: 

• the dispersed phase concentration, 

• viscosity ratio, 

• interfacial tension, 

• continuous phase viscosity, 

• shear stress. 

• Stretching and orienting the spherical particles in the elongational flow fields at the extruder exit (blowing and drawing) form elongated structures. The morphology is influenced by: 

• initial domain size, 

• polymer elasticity, 

• minor component percentage, 

• draw ratio.

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