Untersuchungen zur Phasenmorphologie und deren Einfluss auf das viskoelastische Verhalten von Elastomerblends
Mechanische Eigenschaften von metallischen Werkstoffen und ihre mikrostrukturellen Ursachen
Polymermaterialien
Zusammenfassung der Projektergebnisse
The project delivers new insight into the structure and properties of unfilled and filler reinforced elastomer blends, which is mainly based on the developed analytical as well as numerical models. Regarding numerical modelling, we developed two pipelines for deriving complex blend morphologies with smoothly varying phase-field data. While the first approach enables the derivation of own structures for the elastomer blends, the second approach is based on microscopic images. The diffuse morphologies are used as an input for the material properties, for which we proposed a rheological model combining two generalized Maxwell models based on the phase-field data. Both the derivation of blend morphologies and the proposed material model were successfully implemented in an advanced FEA tool providing all the necessary computational features required for the simulations. Our numerical investigations of the viscous material behaviour of the complex phase morphologies reveal a good agreement with the experiments. It could be shown that the developed diffuse morphology is indeed superior to the sharp one, as the former leads to qualitatively more reasonable curves in the frequency domain, inhibiting two glass transitions. Similar observations could be made based on our 3D studies, for which we used morphologies derived from scratch. The results obtained from image processing AFM data demonstrate that the developed method allows for preparing representative volume elements of filled elastomer blends, as well. Since assigning the filler content to polymer phases is sparsely addressed in the literature, there is no standardized method on defining such blend structure. The filler dominantly distributes to the SBR phase, which is in line with the literature. Consequently, highly-filled blends consisting of low-filled NR and even higher-filled SBR exceed the limits of available dynamic mechanical data, then causing extrapolation problems in computing dynamic moduli. The majority of results is physically reasonable, including the filler content-independent glass transition and the ascending moduli with increasing filler content. The behaviour of dynamic moduli between the glass transitions is of particular interest when investigating elastomer blends and often attributed to the interphase. The time scale of chain diffusion in the interphase is determined by the chain length and the monomeric friction coefficient, which is evaluated by two different techniques based on the Rouse theory. The data obtained from the measured viscosity are less convincing, since the Rouse model underestimates the molar mass dependence of viscosity. More reasonable values are obtained from the predicted power law behaviour in the glass transition regime, which allows for an estimation of monomeric friction coefficient also for the technical elastomers with broad molar mass distribution.
Projektbezogene Publikationen (Auswahl)
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Influence of phase morphology on viscoelastic properties of rubber blends. Constitutive Models for Rubber XII, 121-126. CRC Press.
Müller, Martin; Lang, Andrej; Klüppel, Manfred & Giese, Ulrich
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The influence of a diffuse interphase on the viscoelastic behavior of rubber blends. Constitutive Models for Rubber XII, 127-132. CRC Press.
Voges, J.; Juhre, D.; Müller, M.; Lang, A. & Klüppel, M.
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Fundamental approach to build viscoelastic master curves for heterogeneous elastomer blends. Constitutive Models for Rubbers XIII, 134-139. CRC Press.
Lang, A.; Müller, M.; Klüppel, M.; Giese, U.; Voges, J. & Juhre, D.
