Effects of Dissolved Gas on Viscoelastic Scaling and Glass Transition Temperature of Polystyrene Melts

Abstract

is used to predict viscoelastic scaling factors describing the effect of dissolved gas content on the viscosity curves of polystyrene melts swollen with dissolved carbon dioxide and dissolved 1,1difluoroethane. The predictions of the theory are compared to viscoelastic scaling factors measured by Kwag et al. 2 (J. Polym. Sci. B: Polym. Phys. 1999, 37, 2771 for each system at 150 and 175 °C, at concentrations up to 10 wt % of dissolved gas, and pressures ranging up to 22 MPa. The agreement between the theory and experiments is very good for the polystyrene-CO 2 system but only fair for the polystyrene-1,1-difluoroethane system. The experimental viscoelastic scaling factor values are also interpreted with the WLF equation to estimate the change in the underlying glass transition temperatures of the polystyrene-gas mixtures. The glass transition temperatures estimated from these rheological data are in very good agreement with values directly measured for polystyrene-CO 2 mixtures and with the theory of Condo et al. 3 (Macromolecules 1992, 25, 6119).

Quantifying Polymer Swelling Employing a Linear Variable Differential Transformer: CO2 Effects on SBS Triblock Copolymer

“…From prior work it is known that the T g of PS decreases with increasing CO 2 content. [10,16,17] Based on the work of Wang et al, we estimated the T g of PS at 134 bar to be %35 8C. [10] Thus, at 45 8C the PS phase cannot physically crosslink SBS effectively.…”

Experimental and numerical studies on the effects of pressure release rate on number density of bubbles and bubble growth in a polymeric foaming process

“…The zero shear viscosity was used as the value of viscosity. Although CO 2 -induced viscosity depression has been reported by many authors (Elkovitch et al, 2000(Elkovitch et al, , 2001Han et al, 2002;Kwag et al, 1999Kwag et al, , 2001Lee et al, 2000;Royer et al, 2000;Utracki and Simha, 2001;Xue and Tzoganakis, 2003), its effect on bubble growth may be limited (Chen et al, 2006). The zero-shear viscosity used in this study was not measured under a high-pressure CO 2 condition (Table 1).…”

Extensional Flow Properties of Externally Plasticized Cellulose Acetate: Influence of Plasticizer Content

“…Adequate melt viscosity is necessary to maintain sufficient melt pressure in the die and to prevent premature foaming [1]. In this context, it has to be considered that the dissolved blowing agent (BA) can act as plasticizer, which causes a considerable reduction in the viscosity of the polymer melt [2][3][4][5]. If melt pressure is lower than the solubility pressure required for complete dissolution of the BA in the melt, early nucleation and premature foaming in the die can occur, causing poor morphology and surface quality of the foam [1,6,7].…”