TY - ABST

T1 - Are Entangled Polymer Melts Different From Solutions?

A1 - Huang,Qian

A1 - Mednova,Olga

A1 - Rasmussen,Henrik K.

A1 - Skov,Anne Ladegaard

A1 - Almdal,Kristoffer

A1 - Hassager,Ole

AU - Huang,Qian

AU - Mednova,Olga

AU - Rasmussen,Henrik K.

AU - Skov,Anne Ladegaard

AU - Almdal,Kristoffer

AU - Hassager,Ole

PY - 2012

Y1 - 2012

N2 - The possible existence of a qualitative difference on extensional steady state viscosity between polymer melts <br/>and polymer solutions is still an open question. Recent experiments [1-4] showed the extensional viscosity of both <br/>polymer melts and solutions decayed as a function of strain rate with an exponent of -0.5. When the strain rate <br/>became higher than the order of inverse Rouse time, the polymer solutions showed an upturn [1, 4]. However, in <br/>the same regime for polymer melts, the experiments were contrary: some of the experiments showed an upturn <br/>[4, 5], while others did not [2, 3]. <br/>In order to further investigate the extensional steady state viscosity of polymer melts, we carefully synthesized two <br/>monodisperse polystyrenes with molar masses of 248 and 484 kg/mole. The start-up and steady uniaxial <br/>elongational viscosity have been measured for the two melts using a filament stretching rheometer. We then <br/>compared the measurements with the bi-disperse polystyrene melts made from the above two polymers. The <br/>influence and sensitivity of impurities were studied by adding different percentages of 484k into 248k polystyrene <br/>melt. Furthermore a polydisperse polystyrene with weight average molecular weight 230 kg/mole was also <br/>measured for comparison. Possible reasons for the differences shown in the previously mentioned experiments <br/>are discussed.

AB - The possible existence of a qualitative difference on extensional steady state viscosity between polymer melts <br/>and polymer solutions is still an open question. Recent experiments [1-4] showed the extensional viscosity of both <br/>polymer melts and solutions decayed as a function of strain rate with an exponent of -0.5. When the strain rate <br/>became higher than the order of inverse Rouse time, the polymer solutions showed an upturn [1, 4]. However, in <br/>the same regime for polymer melts, the experiments were contrary: some of the experiments showed an upturn <br/>[4, 5], while others did not [2, 3]. <br/>In order to further investigate the extensional steady state viscosity of polymer melts, we carefully synthesized two <br/>monodisperse polystyrenes with molar masses of 248 and 484 kg/mole. The start-up and steady uniaxial <br/>elongational viscosity have been measured for the two melts using a filament stretching rheometer. We then <br/>compared the measurements with the bi-disperse polystyrene melts made from the above two polymers. The <br/>influence and sensitivity of impurities were studied by adding different percentages of 484k into 248k polystyrene <br/>melt. Furthermore a polydisperse polystyrene with weight average molecular weight 230 kg/mole was also <br/>measured for comparison. Possible reasons for the differences shown in the previously mentioned experiments <br/>are discussed.

ER -