Elastic Behaviour of Polymer Melts

Swelling Ratios Due to Shear Stresses (a) Long Capillary 

So from the deflnition of swelling ratio and using the subscripts S and R to denote Shear swelling in the Radial direction then 

Assuming that the shear strain, yr, varies linearly with radius, r, then 

When the polymer melt emerges from a die with a rectangular section there will be swelling in both the width (T) and thickness (H) directions. By a similar analysis to that given above expressions may be derived for the swelling in 

Equations (5.51), (5.52) and (5.53) can be cumbersome if they are to be used regularly so the relationships between swelling ratio and recoverable strain are often presented graphically as shown in Fig. 5.11. 

---