Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster: Rheology (joint focus with DRG)
CPP 37.4: Poster
Donnerstag, 29. März 2012, 18:45–19:45, Poster A
Gap dependence of the trim distance in parallel plate rheometry — •Roman Sebastian Rittberger1,2 and Gerhard Eder2 — 1Transfercenter für Kunststofftechnik GmbH, Wels, Österreich — 2Institute of Polymer Science, Johannes Kepler Universität, Linz, Österreich
Calculations in parallel plate rheometry rely on cylindrical sample shapes. However, trimming excessive material after sample loading often leads to a slightly dinted rim. Consequently the gap is lowered additionally by the trim distance δ to achieve cylindrical sample geometry. Thus gap dependence of the trim distance δ for a given measurement geometry and material has to be known a priori.
For this investigation polymer samples were melted in the rheometer and the gap was set to trim position HT. After thermal equilibration excessive melt was removed with an applicator and the samples were quenched to solidify for following weighing. The trim distance is modeled by approximating the rim geometry as parabola and assuming the depth of dint Δ r = Δ r* HT. The model also accounts for potential gap errors. Doing regression analysis on a series of trim positions gives the material specific constant Δ r* and the gap error of the measuring system.
The dependence of the trim distance δ on the trim position HT was found to be quadratic (higher terms can be neglected). Plotting δ / HT versus HT / R leads to a unified representation, which can be deployed for plates with arbitrary radii. The only parameter left is the constant Δ r*, solely depending on the materials properties.