The startup and steady uniaxial elongational viscosity have been measured for two monodisperse polystyrene melts with molecular weights of 52 kg/mole (PS52K) and 103 kg/mole (PS103K), and for three bidisperse polystyrene melts. The bidisperse melts consist of PS103K or PS52K and a monodisperse polystyrene melt with a molecular weight of 390 kg/mole (PS390K). The measurements have all been preformed on a Filament Streching Rheometer (FSR) equipped with an oven: A cylindrical test sample is placed between two parallel, circular plates and stretched. A load cell measures the transmitted force, and a laser monitors the central diameter of the stretched filament. Our rheometer is located in a thermostated environment. Notice, a camera to ensure a centered sample during measurement monitors the location of the central necking in the filament. The distance between the end plates is adjusted online (closed loop proportional regulator) using the laser in such a way that the stretch rate at the neck is kept constant. The rheometer has been described in more detail in (A. Bach, H.K. Rasmussen and O. Hassager, Journal of Rheology, 47 (2003) 429). PS390K show a decrease in the steady viscosity as a power-law function of the elongational rate (A. Bach, K. Almdal, H.K. Rasmussen and O. Hassager, Macromolecules 36 (2003) 5174). PS52K and PS103K show that the steady viscosity has a maximum that is respectively 100% and 50% above 3 times the zero-shear-rate viscosity. The bidisperse melts show a significant different behavior. The steady elongational viscosity of PS390K blended with PS52K exhibit a maximum in the steady viscosity. It is up to 700% above 3 times the zero-shear-rate viscosity. The maximum for the blend of PS390K and PS103K is not as large though significant higher than the maximum observed in the PS103K melt. The maximum in the steady uniaxial elongational viscosity seems to relates to the amounts of anisotropy in the extended melt.
|Title of host publication||Abstract of the 77th Annual SOR Meeting|
|Publication status||Published - 2005|
|Event||77th Annual Meeting of the Society of Rheology - Vancouver, Canada|
Duration: 5 Nov 2005 → …
Conference number: 77
|Conference||77th Annual Meeting of the Society of Rheology|
|Period||05/11/2005 → …|