Berlin 2012 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Focus: Rheology II (joint focus with DRG)

CPP 38.8: Talk

Friday, March 30, 2012, 11:30–11:45, C 130

Investigation of the Miscibility and Phase Separation of Molten PP/PE Blends via Rheometry — •Matthias Mihalic and Alois Schausberger — Institute of Polymer Science, Johannes-Kepler-Universität, A-4040 Linz, Austria

Rheometry is a powerful tool for the detection of phase separation in molten polymers and thus for the investigation of the solubility of each component in a mixture. The sample preparation for such measurements typically involves one or several crystallization steps, which in turn induce phase separation in the sample. Neither will this phase separation be balanced out by diffusion in the melt, nor is the rheometer suitable to be used as a compounder. Consequently, one might get somewhat distorted results. Therefore it seems desirable to avoid any crystallization between the compounding and the rheological characterization of a blend.

To this end, an experimental set-up was designed such that after compounding, the molten blends are directly injected into the measuring cell of a rheometer, where the dynamic moduli are determined.

In case of miscibility, the relaxation time spectrum of a blend can be simply calculated from the combined molar mass distributions of the components. Otherwise, phase separation will be reflected in the spectrum of the mixture obtained from dynamic mechanical data. The measurement results are further analyzed using the model of Gramespacher and Meissner in order to gain information about the phase structure of the blend. In addition, by preparing blends of different concentrations, the boundaries of miscibility are checked.