Dresden 2017 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 5: Polymer Networks and Dynamics I: Elastomers and Magnetic Materials

CPP 5.1: Hauptvortrag

Montag, 20. März 2017, 10:15–10:45, ZEU 255

A Combined Rheological and Dielectric Analysis of Filler Networking in Elastomer Nano-Composites — •Manfred Klüppel — Deutsches Institut für Kautschuktechnologie e.V., Eupener Str. 33, D-30519 Hannover, Germany

The dynamics of filler networking (flocculation) in carbon black filled elastomer composites is investigated by dielectric relaxation spectroscopy during oscillatory shearing in a plate-plate rheometer. It is demonstrated that during heat treatment at low strain amplitude, a pronounced filler networking takes place in rubber melts leading to a simultaneous increase of the shear modulus and dc-conductivity. Two relaxation times, obtained from a Cole-Cole fit of the dielectric spectra, are identified, which both decrease strongly with increasing flocculation time. This behavior is analyzed in the frame of fractal network models. During filler networking, a universal scaling behavior holds between the conductivity and the corresponding high frequency relaxation time, which fits all the measured data. It is demonstrated that the underlying basic mechanism is a change of the correlation length of the filler network, i.e. the size of the fractal heterogeneities. This decreases during filler networking due to the formation of additional conductive paths. The same universal scaling behavior is found for temperature dependent dielectric measurements of the cured systems, which are heated from room temperature up to 200 °C. Thereby, the conductivity decreases and the relaxation time increases, indicating that the filler network breaks up randomly due to the thermal expansion of the rubber matrix.