Experimental Investigation on the Shearing Rheology of Dilute Polystyrene in Single and Mixed Solvent Systems

• Main Authors: Hing-Hung, Lin, 林信宏
• Other Authors: Chi-Chung, Hua
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/87992379043945331634

碩士 === 國立中正大學 === 化學工程研究所 === 92 === We performed systematical experimental investigations on the shearing rheology of dilute polystyrene in single, highly viscous (DOP) as well as in mixed, highly viscoelastic (DOP plus short-chain polystyrene) solvent systems. Following the usual shear thinning, a pronounced shear thickening followed by a second shear thinning was observed at even higher shear rates for both solvent systems. Significantly, this phenomenon is in excellent accord with the predictions based on dumbbell/bead-spring models that simultaneously consider the effects of hydrodynamic interactions, excluded volume, and finite extensibility, and this appears to be the first time that such a comprehensive rheological feature in shear flows has been experimentally verified. The previous phenomenon, nevertheless, vanishes for the mixed solvent system if there is only a moderate amount of short-chain polystyrene being added; namely, in this case one observed only a simple shear-shinning behavior. This was subsequently ascribed to the poor solvent quality with the addition of short-chain polystyrene, as suggested by earlier low-shear-rate viscometric measurements and light scattering data. This apparent change in solvent quality has been further verified here by the scaling behavior of the relaxation time constants evaluated at the onset of the first shear thinning, as well as by the molecular weight dependence of the measured intrinsic viscosity.