Dresden 2006 – wissenschaftliches Programm

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CPP: Chemische Physik und Polymerphysik

CPP 9: SYMPOSIUM Disperse Polymer Systems II

CPP 9.1: Hauptvortrag

Dienstag, 28. März 2006, 14:00–14:30, ZEU 160

Rheology and Structure Kinetics of Filled Polymer Nanocomposites and Networks — •Gert Heinrich — Leibniz Institute of Polymer Research Dresden, Hohe Strasse 6, D-01069 Dresden, Germany

Dynamic-mechanical and rheological studies provide an excellent access to the morphology and dynamics of complex filled polymers and to tests of corresponding models. Based on several dynamic-mechanical and shear flow experiments we discuss common features of structural filler reorganization in diverse filled elastomers and in polymer nanocomposites consisting of a thermoplastic melt (LDPE) and nanofillers (Mg/Al based Layered Double Hydroxide). In the elastomer case the discussion is possible when studying the kinetics of the modulus recovery with experimental set-ups where the stiffness response on repeated amplitude steps is measured. In the stress growth experiment the nanocomposites exhibit a pronounced non-linear behaviour observed as a shear overshoot. The time, at which the overshoot appears, decreases as the LDH loading increases. This effect can be described using the Wagner model, in which the non-linearity parameter increases with the particle loading and the relaxation time of the system decreases with the increase in shear rate. Additionally, in the high loaded nanocomposites, we observe shear oscillations presumably caused by the presence of a LC texture formed by the anisotropic filler particles. We propose that LDH particles in the PE melt are organised in domains (perhaps, orientational) which size is drastically diminished upon shear application.