Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 64: Flow-Induced Structures in Complex Fluids (with DRG, Deutsche Rheologische Gesellschaft, and DY)
CPP 64.1: Vortrag
Donnerstag, 19. März 2015, 09:30–09:45, C 264
Rheology of PMMA solutions - the role of maximum stretch ratio in the nonlinear regime — •Sara L. Wingstrand1, Qian Huan1, Nicolas J. Alvares2, and Ole Hassager1 — 1Technical University of Denmark, Kgs Lyngby, Denmark — 2Drexel University, Philadelphia, USA
This work concerns linear and nonlinear rheology of poly(methyl methacrylate) (PMMA) solutions. Oligomeric methyl methacrylate is used as solvent. The concentration of polymer in solution has been adjusted, such that the maximum stretch ratio (λmax) is equal to that of a polystyrene melt of 285 kg/mol (PS-285k). Accordingly, the molar mass of PMMA has been selected to obtain the same number of entanglements (Z) as the PS-285k. The solutions are characterized both in small amplitude oscillatory shear and in uniaxial extension, where the influence of λmax and Z is investigated. It is found that the linear behavior of the PMMA solutions obey the tube model with a dilution exponent of 1. Consequently, as intended, the normalized dynamic moduli of the solutions overlap those of PS-285k. In the nonlinear regime the PMMA solutions exhibit a greater resemblance with PS-285k, than other polymers having same Z but significantly different values of λmax. Nevertheless, the observed trend in extensional steady state viscosity vs. strain rate differs. Consequently we conclude that introducing λmax in the tube model to enable application in the nonlinear regime, is not sufficient for obtaining a unifying model valid for polymer melts and solutions together.