Rheology and Fourier transform rheology on water-based systems

Autori

• Christopher Klein

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• Libri di testo
• Libri di testo universitari

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This thesis investigates the influence of shear fields on water-based systems, focusing on the non-linear rheological behavior of spherical and rod-like particles through Fourier-Transform rheology under LAOS conditions. Two types of polystyrene dispersions, each with a solid content exceeding 0.3, were synthesized as model systems for spherical particles. Differences in polydispersity and Debye-length led to variations in rheological behavior. Both dispersions exhibited a similar increase in the intensities of odd higher harmonics, as predicted by a model, although some second harmonics appeared unexpectedly. A novel analysis method was developed to decompose the time domain signal into four characteristic functions corresponding to rheological phenomena, with potential negative interference among Fourier components. FD-virus particles served as a rod-like model system, demonstrating highly non-linear behavior at concentrations below 1% wt. The predictions for higher harmonics' dependence on strain amplitude were accurate at large amplitudes but less so at smaller ones, aligning with existing theories for rod-like particles. Enhancements to an existing rheo-optical setup included a 20-fold reduction in background birefringence and a 24-fold increase in time resolution, allowing for a combination of FT-rheology and rheo-optics. The impact of a constant shear field on zinc oxide crystallization in the presence of a polymer was

Lingua: Inglese

Pubblicato: 2008

(In brossura)