Strukturaufklärung mittels Neutronen- und Röntgenstreuung wie rheologische Untersuchungen gescherter Kolloiddispersionen
This Paper is concerned with charge stabilized concentrated polymer dispersions. The presented shear-model is suitable for describing the dispersion at rest and under shear. Rheology as well as small angle neutron and synchrotron x-ray scattering is considered. Under shear particles are ordered in random stacked hexagonal layers. The scattering intensity along the white Bragg rods ((h-k)=3n±1) shows a maximum at l = 0.5. The layers distance c can be written as c=a.(2/3)**0.5, a is the particle distance within the layer. Starting with the shear ordered sample at rest, hexagonally arranged Bragg reflection are observed. As the shear disk starts rotating a torque is exerted on the layers. As long as the shear stress is below yield stress layers are distorted. In this case the scattering intensity along the white Bragg rods shows a maximum at l < 0.5, hence the layers distance c is extended and elastic properties are observed. While the layers are distorted, they remain hexagonally ordered. Sliding layers occur as the shear stress exceeds yield stress, the layers begin to correlate and Bragg reflections reappear again. A farther increase of the shear rate results in the layers taking up a random stacking order. The distance of the layers increases while shear thinning occurs. The more the shear rate is increased the intensity distribution on the white Bragg rods (distinct term) decreases. To obtain the intensity distribution along Bragg rods two possible orthogonal rotations could be performed. a-Rotation is obtained, when the sample kept about the flow direction. The ß-Rotation will be observed by kipping the sample about a direction perpendicular to the flow direction as performed by translation of the couette cell with respect to beam. In this case the two Bragg rods (-1,1) and (1,-1) as well as all rods (n,-n) and (-n, n) are positioned on the rotation axis. Their intensity is useless for explaining the structure in the dispersion.
info:eu-repo/classification/ddc/530, Physik, Dispersionskolloid, Scherung, Fließverhalten, Röntgenstreuung, Neutronenstreuung
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