Dresden 2003 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 20: POSTER A

CPP 20.17: Poster

Montag, 24. März 2003, 19:00–21:00, ZEU/250

High-temperature rheo NMR on polymer melts — •Ulrich Scheler and Antje Gottwald — Institute for Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden

Polymer melts possess a complex flow behaviour. Non Newtonian and viscoelastic properties lead to unconventional response to applied shearing forces. There is a basic interest in understanding these processes as well as an interest generated from applications to optimise the processing of polymers. Pulsed field gradient NMR in combination with NMR imaging allows the direct measurement of velocity profiles, i.e. spatially resolved velocity distributions. Various NMR parameters as chemical shift and relaxation times can be used to gain contrast or to separate the velocities of different components of the sample. Rheological NMR uses these possibilities to investigate flow processes in rheological devices like Couette cells or rheo cells with cone/plate geometry. The method gains complementary results to common rheometers, which measure integral parameters like viscosity, torque and so on. Up to now rheo NMR was restricted to room temperature. High temperatures needed to melt technical relevant polymers require an adequate shielding of the NMR magnet which has to be kept near room temperature. Here we present a high-temperature rheo NMR cell. It allows measurements up to 200oC. In a Couette geometry measurements on commercial PVC and physically crosslinked polyamidines have been performed to demonstrate the potential of the cell. Additionally rotors with non cylindrical shape have been used to create areas of different shearing rates inside the cell.