Localized flow birefringence of polyethylene oxide solutions in a two roll mill

Experimental observations are reported of the behavior of solutions between two rotating parallel rollers where the form of the flow field between corotating rollers corresponds to that of a col which has nonorthogonal asymptotes. The obliquity of the asymptotes of the flow gives a direct measure of the relative magnitude of the constituent pure shear and rotational components of the flow field. Flow birefringence observations of polyethylene oxide solutions between the corotating rollers show that molecular orientation is limited to a highly localized region near the “outgoing” asymptotic sheet of the flow field in accordance with the predictions of a “persistent extensional flow” analysis presented. Counterrotating rollers show no flow birefringence also as expected. The behavior of polymer solutions and Newtonian fluids are compared. With increasing strain rate using corotating rollers the obliquity of the asymptotes of the flow remains constant for the Newtonian fluid but changes significantly for the polymer solution.