Flow of viscoelastic polymeric melts through converging ducts

Summary

An experimental study has been carried out to better understand the flow behavior of viscoelastic polymeric melts in a converging channel which consists of two nonparallel planes. For the study, measurements were taken of both stresses and velocities, the former by means of the flow birefringence technique and the latter by means of streak photography. The material used was polystyrene. A comparison was made of the stress-birefringent patterns obtained in the present study with those obtained in an earlier study byHan andDrexler, who used a slit die having a tapered entrance. It has been found that both stresses and velocities in the converging flow field of polymeric melts do not exhibit any noticeable evidence of secondary motion, contrary to the theoretical prediction made by earlier investigators. The apparently unnoticeable secondary motion in the present study may be attributable to the extremely slow motion of the polymeric melts investigated. Also carried out was a theoretical analysis of converging flow. This was essentially the same as that carried out earlier byHan andDrexler, using a modified second-order fluid model which assumes that all three material functions depend on the second invariant of the rate of deformation. A comparison was made of the experimentally determined stress distributions with the theoretically predicted ones.