<p> Since Newton's definition of viscosity does not lead to a useful description of non-Newtonian flow, two other model liquids, the Maxwell liquid and the Prandtl-Eyring liquid are discussed. Equations describing the flow behaviour of these liquids in narrow capillaries are derived and discussed. </p> <p> A thorough analysis is given of corrections that are, or may be, necessary in capillary viscometry, and the influence of non-Newtonian flow on these corrections is discusses, both for cylindrical and spherical bulbs. </p> <p> The significance of measurements of non-Newtonian flow in dilute solutions of macromolecules is discussed in terms of recent theories. It is shown that a capillary viscometer has inherent limitations for such measurements, but that a properly designed capillary viscometer can give precise and reliable data at shear rates down to 50 sec^-1, provided that the system is not too shear-dependent. </p> <p> A new variable shear capillary viscometer-- a modification of the Ubbelohde suspended level viscometer-- is describes. It was designed to be rugged, convenient and precise, to eliminate or minimize the kinetic energy correction and surface tenison effects, and to permit dilution of a solution while in the instrument. Three different viscometers of this type have been constructed, calibrated and tested, and proved sound in design and convenient in use. </p> <p> The usefulness of the viscometers has been demonstrated in three diverse investigations: (i) the shear dependence in aqueous solutions of a high molecular weight dextran, (ii) the temperature dependence of the zero-shear intrinsic viscosity in a good solvent of a very high molecular weight fraction of polystrene, (iii) the shear dependence of the interaction coefficient k' in the systems polystyrene-toluene and poly(n-octyl-methacrylate). </p> / Thesis / Master of Science (MSc)

The objective of the research was to develop fundamental understanding of the process of deposition of complex mixtures by the inkjet method. The rheological properties and DOD drop formation dynamics of carbon black pigmented inkjet inks were investigated. It was found that the suspension microstructure responses to bulk motions, leading to shear rate and time dependent shear viscosity. However, DOD drop formation dynamics of highly pigmented inkjet ink and pure Newtonian fluid is similar even though shear rate up to 105 s-1 exists during inkjet jetting process. A proposed explanation for these observations is that the shearing time during DOD drop ejection is insufficient for changing and stabilizing the microstructure of the suspension. The effects of signal amplitude and jetting frequency on DOD drop formation dynamics of pure Newtonian fluids were investigated. A transition of DOD drop formation dynamics when the inkjet nozzle is switched from idle to jetting was identified. A qualitative investigation of DOD drop impaction and post-impaction behavior on inkjet paper and textiles was carried out. Dynamics of DOD drop accumulation and spreading on the substrates and final ink distribution show drastic differences between these two substrates.