Extensional flow dynamics of polystyrene melt

A linear polystyrene melt with broad molecular weight distribution (CAS 0993-53-6 from Aldrich) was characterized in extensional flow using a filament stretching rheometer. A series of measurements were performed, including (1) the startup of uniaxial extensional flow until steady state; (2) the strain controlled reversed (i.e., biaxial) flow following the startup of uniaxial flow; and (3) stress relaxation (i.e., keeping the strain unchanged) also following the startup of uniaxial flow. The measurements were compared with the model by Narimissa and Wagner [J. Rheol. 60, 625–636 (2016)]. Good agreements at low extension rates and low strain values were observed. Higher deviations were observed at high rates under steady state conditions as well as during stress relaxation and reversed flow.