Extensional viscosity of polystyrene solutions in dilute region

Extensional viscosities eta(e)((epsilon)over dot) of polystyrenes (PS) with high molecular weights in benzyl butyl phthalate (BBP; a good solvent for PS) and dioctyl phthalate (DOP; a theta solvent for PS) were studied in the dilute region for viscosity as a function of the extensional rate with an opposing jets extensional rheometer. The eta(e)((epsilon)over dot) data obtained with use of different orifice geometries agree with each other within experimental errors. The extensional viscosity at low epsilon limit, eta(e)(o) is about three times larger than the corresponding zero-shear viscosity in accordance with Trouton's rule. In high epsilon region, the extensional-thickening was observed for all the solutions. The critical extensional rate epsilon* at which the eta(e)(epsilon) deviates from eta(e)(o) is confirmed to be related to the longest relaxation time of the solutions.