Berlin 2012 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 38: Focus: Rheology II (joint focus with DRG)
CPP 38.5: Vortrag
Freitag, 30. März 2012, 10:45–11:00, C 130
Carbon dioxide plasticized polymer melts - An interpretation by means of the free volume concept — •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
CO2 is a well established physical foaming agent for polymers. However, dissolving carbon dioxide under pressure strongly affects the rheological properties of the melt. The influence of pressure and of low molecular weight diluents (M<Mc) on the material functions are determined via oscillatory measurements. Therefore, a common plate-plate-system in a pressure cell is used. Relations based on the free volume concept are used to interpret the experimental results. In case of linear polymers (PS, PP) the time-concentration-superposition is simple. The mastercurve is created by shifting the dynamic moduli of the CO2-diluted polymer melt to the dynamic moduli of the neat polymer. The shift factors obtained are corrected by the effect of pressure. In addition, by use of the generalized Doolittle relation the concentration dependent horizontal shift factors ac are calculated. The rheological properties of carbon dioxide plasticized polymer melts as well as the molar plasticizing activity A of an additive can be predicted.
Independently of the horizontal shift ac, an additional shift bc on the modulus axis is found by a vanGurp-Palmen plot. The relation bc=w2 is applied and the vertical shifts are calculated. w is the weight fraction of the entangled polymer.