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Title: Investigation of the Non-Newtonian/Newtonian Immiscible Polymer Blend Rheological Behavior Using Large Amplitude Oscillatory Shearing Flow
Authors: Noureyah A. Barakat 
Supervisor: Dr. Abdulwahab S. Almusallam
Keywords: Oscillatory : Newtonian
Issue Date: 2018
Publisher:  Kuwait university - college of graduate studies
Abstract: Large amplitude oscillatory shear (LAOS) was carried out on model Non- Newtonian/Newtonian immiscible polymer blend. The blend was composed of Polydimethylsiloxane (PDMS) as a minor phase and Polybutadiene (PBd) as a matrix phase. The PBd is an elastic “Boger Fluid” that was made by dissolving high molecular weight Polybutadiene into low molecular weight Newtonian Polybutadiene. The immiscible polymer blend was studied at compositions of 2.5%, 5%, 7.5% and 10% of high molecular weight PBd that was mixed with the Newtonian (PBd) resulting in four samples of Boger fluids. The final blend was made by mixing the four prepared Boger fluids as a matrix phase with droplet phase (PDMS) of percentage of 20% droplet and 80% Matrix phase. The Average droplet size was calculated by fitting the Palierne model to experimentally obtained small amplitude oscillatory shear data. The stresses from LAOS test were Fourier-Transformed to stress harmonics and then compared with (Daffallah, 2018) study that was conducted for the case where the non-Newtonian component was the droplet phase. As a result, the analyzed results in both studies indicate the same behavior of both blends and identical droplet size at the same viscosity ratio blends of the high molecular weight Boger fluid. First, third and fifth harmonics were obtained from LAOS test and for analysis, quantitative nonlinear coefficient for the third and fifth harmonics were obtained. As results, the coefficients indicate decrease in value as the strain amplitude increases. Further analysis and for coefficients data were obtained by multiplying the coefficients to viscosity ratio of the four sample blends to the power 0.5, as 0.5 was found to be the best fit to have the lines overlap. Note that the seventh harmonics was eliminated since it has shown no accuracy. Also another analysis was made to track the non -linear behavior using Lissajous loop at 300%, 1000% and 1600% strain amplitude, which imply evolution in the shape of the distorted stress waveforms can be related with systematic changes in the internal microstructure of blend the nonlinear stresses born by the major phase (i.e. Boger Fluid) during LAOS test deformation yet the alteration in the over all structure of the blend is not changing as SOAS tests been run during the test v to ensure that the there is no droplet breakup since the viscosity ratio of the blends is already high, conclude that this change in the microstructure is reversible . At last, LAOS proves to be a sensitive test to investigate and measure the nonlinear viscoelastic behavior of complex fluids, as well as the importance of Fourier Transform (FT) rheology as a technique that is used to analyze such non-sinusoidal stress signals.
Appears in Programs:0640 Chemical Engineering

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