Die swell and melt fracture: Effects of molecular weight distribution

The equations for determining die swell of molten polymers are discussed. The critical conditions for melt fracture and die swell results are combined in order to explain the flow behavior at the onset of instability. It is shown that the factor$$\bar M_z \bar M_{z + 1} /\bar M_w^2 $$ is the most important parameter in die swell and melt fracture studies.