Horizontal extensional rheometry (HER) for low viscosity polymer melts

Extensional flow plays a significant role in many processing operations of polymer melts. However, for slender polymer melts, the measurements of the extensional behavior were strongly limited by the gravitational sagging effect in the Sentmanat extensional rheometry (SER). In this work, a new extensional rheometry was designed to combine the merits of the SER and the rheometric melt elongation rheometer. The new fixture was sufficiently miniaturized to be adapted to the environment chamber of a commercial rotational rheometer. During the measurements, the samples were supported by a base lubricated by oil or microfine polytetrafluorethylene powder to effectively reduce the friction and sagging effects. The new design was validated, using materials with a wide range of viscosities, to extend the low viscosity limit to about two decades compared with the SER fixture, i.e., from ∼104 to ∼102 Pa s.