Water-based dispersions and emulsions are used as model systems for a new rheological data analysis. The application of large amplitude oscillatory shear can be used to generate a high nonlinear response, which is analyzed by Fourier transform (FT)-rheology. The individual higher harmonics appearing in the shear stress response do not have a simple physical interpretation. Furthermore, in the FT analysis used so far the focus was mainly on the third harmonic relative to the fundamental I 3 /I 1 , even if multiple higher harmonics appear, as in the polystyrene dispersions examined here. As a consequence, we propose a new and simple method that considers the whole overtone spectra as a superposition of different overtone spectra of typical nonlinear rheological effects, like strain hardening, strain softening, and shear bands or wall slip. This novel analysis of FT-rheology experiments thus separates the nonlinear mechanical response into the underlying physical phenomena.
Oscillatory shear flow of poly[B-(methylamino)borazine] was studied for suitability as a melt-spinnable material. Shear rheology experiments show that viscosity of molten poly[B-(methylamino)borazine] is
temperature dependent following an Arrhenius-type equation. The high value of the flow activation energy is
caused by the presence of branched chains and cross-linked portions in the polymer network which supply an
intrinsic rigidity to the molecular architecture. Dynamic rheological properties of polymers were measured at
their spinning temperatures as a function of the oscillatory frequency. The frequency dependence of the storage
and loss moduli as well as the damping factor shows that an appropriate ratio of viscosity to elasticity, i.e., 1 <
tan δ < 2.3, is necessary to allow for extrusion while a specific range of elasticity, i.e., 104 < G‘ [Pa] < 3 × 104,
is required for drawing the emerging molten fibers as they solidify into fine-diameter solid filaments without loss
of cohesion.
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