Extensional viscosity of polystyrene solutions in dilute region

Extensional viscosities η _e(ε•) of polystyrenes (PS) with high molecular weights in benzyl butyl phthalate (BBP; a good solvent for PS) and dioctyl phthalate (DOP; a θ 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 η _e(ε•) data obtained with use of different orifice geometries agree with each other within experimental errors. The extensional viscosity at low ε• limit, η ⁰_e is about three times larger than the corresponding zero - shear viscosity in accordance with Trouton's rule. In high ε• region, the extensional - thickening was observed for all the solutions. The critical extensional rate ε• * at which the η _e(ε•) deviates from η ⁰_e is confirmed to be related to the longest relaxation time of the solutions.