Stormer viscosity

Stormer viscosity Mass solids Volume solids PVC... 

Flow properties. Slugging tendency of a fluidized bed increases with increased Stormer viscosity (207). The modified Stormer viscometer used ill this work is provided with a paddle that is rotated in the fluidized bed (by means of a weight attached to a string passing over a system of pulleys). Viscosity is measured by determining the weight required to spin the paddle at 200 r.p.m. Stormer viscosity of the bed increases with decreased gas velocity and with increased size and density of particles. Viscosity of coarse catalyst is decreased, within limits, by addition of fines. 

Problems with Blending. The principle of this approach to optimizing paint rheology is that two paints with the same Stormer viscosity will produce blends with the same Stormer viscosity. In practice, this result does not always occur. For example, a 50/50 HEUR/organoclay-thickened paint made from base paints at 100 KU each may have a Stormer viscosity of only 90 KU. This result often occurs when one of the base paints is very thixotropic. Also, a paint blend may have poorer flow and leveling than either of the base paints. Poor flow indicates that some flocculation may occur during the blending process. 

Base paints should be made, each with a different thickener, at the desired Stormer viscosity. 

Two base paints should be blended, one with a high ICI viscosity and one with a low ICI viscosity, to obtain the desired ICI viscosity. During this process, the Stormer viscosity should remain constant. Typical thickener combinations used are HEUR/cellulosic, HEUR/hydrophobically modified HEC, and HEUR/hydrophobically modified alkali-swellable latex. 

The formulation constants are as follows pigment volume content, 45% volume solids, 36% Stormer viscosity, 90 KU and pH, 9.5. 

Thickening efficiency, for regular cellulose ethers, is strongly linked to the molecular weight. As can be deduced from what has been presented earlier, it is very important to define the shear rate, which correlates with the given thickening efficiency. Generally the Stormer viscosity of 100 KU is used as the reference. 

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