Birefringence relaxation after cessation of flow in injection molding

摘要

The birefringence relaxation after the cessation of flow was studied by observing the birefringence of molten polymer flowing in a thin slit in the direction normal to the shearing plane in an injection molding machine. The birefringence at the wall |(n{sub}11-n{sub}33){sub}w(t)| monotonically decreased to zero as soon as the flow was stopped. The birefringence relaxation after the cessation of flow can be understood as the recovery of the deformation of the linear polymer conformation. The relaxation of the birefringence can be well explained by applying a modified theory of Rouse and Zimm on the deformation and relaxation of polymer conformation in dilute solutions where the maximum relaxation time τ{sub}M is experimentally determined. The calculated values of the relative relaxation of the birefringence |(n{sub}11-n{sub}33){sub}w(t)|/ |(n{sub}11-n{sub}33){sub}w(0)| against t/τ{sub}M give an almost identical curve with the theoretical one.