On the planar extensional viscosity of mobile liquids

An instrument is described in which steady planar orthogonal stagnation flows of the type proposed by Winter [1] are achieved with lubrication. From pressure readings on steady results acceptable Trouton ratios are achieved for a Newtonian sample and results are obtained for a ‘Boger’ fluid showing high levels of extensional viscosity with Trouton ratios approaching 4 in the limit of zero stretch rate.