Rheology of pastes

This lesson is an introduction to the flow behaviour (rheology) of pastes and gels. Examples of such non-Newtonian liquids are ... 

The rheology of pastes, which are highly concentrated suspensions, is very important for the process of extrusion and spheronization to produce pellets. 

Trease, R.E. and Dietz, R.L. (1972) Rheology of pastes for thick film printing. 

A great deal of work has been carried out to improve the rheology of pastes and mechanical strength of the extrudates by using various binders, i>eptizers and surfactants. Some properties of the samples obtained are given in Tfdiles 4 and 5. 

The surface force apparatus (SFA) is a device that detects the variations of normal and tangential forces resulting from the molecule interactions, as a function of normal distance between two curved surfaces in relative motion. SFA has been successfully used over the past years for investigating various surface phenomena, such as adhesion, rheology of confined liquid and polymers, colloid stability, and boundary friction. The first SFA was invented in 1969 by Tabor and Winterton [23] and was further developed in 1972 by Israela-chivili and Tabor [24]. The device was employed for direct measurement of the van der Waals forces in the air or vacuum between molecularly smooth mica surfaces in the distance range of 1.5-130 nm. The results confirmed the prediction of the Lifshitz theory on van der Waals interactions down to the separations as small as 1.5 nm. 

The effect that air-entraining agents have on the rheology of fresh cement pastes can be considered from the point of view of changes due to the admixture itself, and those due to the presence of entrained air. 

Most admixtures of this type do not significantly alter the rheology of cement pastes at early ages. The quicker stiffening of accelerated pastes will, of course, result in higher viscosities at a later age. More complex formulations occasionally include water-reducing admixtures to reduce the water-cement ratio, and their effect will be a function of the water-reducing admixture type and content (see Section 1.3.1). 

This brief account of past investigations is concerned with work on polymer liquid crystals (PLCs), where the majority of work has considered nematic materials. Among the unique rheological responses associated with PLCs are... 

Radiation-Curable, 100% Reactive Pigment Prints The Effect of Paste Rheology on Print Quality... 

Kaolin has a use in plastisol formulations giving good rheological control. Calcium carbonate is also used in this area. An alternative to calcium carbonate, phyllite, has been evaluated. This material, which contains quartz, muscovite and kaolinite, was characterised on the basis of paste viscosity, gelation and fusion behaviour, and mechanical properties (70). 

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