| Schweizer et al. [J Rheol 48 (6):1345-1363, 2004] showed nonlinear step shear rate data for a polystyrene melt (M-w=200 kg/mol, Mw/M-n=1.06, T=175 degrees C). For different rheometers, cone angles, and sample sizes, the delayed normal force rise observed therein relative to a compliance-free reference N-1 (from a thermodynamically consistent reptation model) is shown to depend on rheometer compliance characterized by the instrument stiffness K-A. K-A can be obtained from mapping N-1 on the measured N-1,N-meas. or directly from mechanical contact measurement with a mismatch of 20-30%. The ranking of the stiffnesses found is K-A(RMS 800)> K-A(MCR 300)> K-A(ARES LR2). Once K-A is known, N-1meas.-data can be corrected by solving the ill-posed Volterra equation involved in it. The correction shown for experiments with the 0.15-rad cone angle gives very good results. The characteristic decay time of the normal force after cessation of flow scales linearly with the axial response time t(a) calculated from KA, cone angle, and sample radius. The torque decay time is practically independent of t(a).
for LaTeX users @article{TSchweizer2006-45,
author = {T. Schweizer and A. Bardow},
title = {The role of instrument compliance in normal force measurements of polymer melts},
journal = {Rheol. Acta},
volume = {45},
pages = {393-402},
year = {2006}
}
\bibitem{TSchweizer2006-45} T. Schweizer, A. Bardow,
The role of instrument compliance in normal force measurements of polymer melts,
Rheol. Acta {\bf 45} (2006) 393-402.TSchweizer2006-45
T. Schweizer, A. Bardow
The role of instrument compliance in normal force measurements of polymer melts
Rheol. Acta,45,2006,393-402 |
mk@mat.ethz.ch
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