Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 37: Poster: Rheology (joint focus with DRG)
CPP 37.2: Poster
Donnerstag, 29. März 2012, 18:45–19:45, Poster A
The reversibility of modifications created by processing linear and long chain branched polypropylene melts — •Bernadette Duscher1,2, Alois Schausberger2, and Wolfgang Stadlbauer1 — 1Transfercenter für Kunststofftechnik GmbH, Franz-Fritsch Str. 11, A-4600 Wels — 2Johannes Kepler University, Altenberger Str. 69, A-4040 Linz
The rheological properties of long chain branched polypropylene (LCB-PP) and of its blends with linear PP (L-PP) are strongly affected by processing time, temperature, machining method and even screw configuration. The resultant modification and its reversibility are investigated by means of rheological experiments in shear and elongation. In addition, the flow activation energies (Ea) of process-modified samples are determined in order to describe the entanglement state.
Three different processing methods (measuring mixer, twin-screw extruder with varying screw set-ups) and varying processing parameters have been used. The reduction of dynamic moduli and Ea depends on the operational demands the polymer blend has passed. By dissolving process-modified samples, an equilibrium state is created and the activation energies as well as the rheological properties of the blends are determined. The dynamic moduli do not recover totally but superimpose in a limit function. However, after dissolving Ea of the samples equal those of neat, dissolved and untreated samples. By determining strain hardening behavior, it is shown that the smaller the strain rates are, the higher the difference between the process-modified samples and its dissolved equivalents is.