Viscometer Frequently Asked Questions

Rheology determines the flow and deformation of matter. Viscometric measurements, as part of the science of rheology, characterize the properties of materials by providing values of absolute viscosity in flow curves. When recorded, such a flow curve is called a rheogram. The uses of such measurements are helpful in: Product research and development Process development Quality control Application of viscometric measurements provides guidelines in: Optimizing processability Developing formulations for better runnability and improved productivity Proper interpretation of the data can reduce the rate of rejects while keeping production and formulation development cost to a minimum. Their unique feature is the capability to model real situations within a wide range of shear rates. The overall objectives of viscometric measurements are: Material characterization Understand flow performance To solve application process problems Viscometric measurements are valuable in quality control, alone or in conjunction with compatible tests.

The objective of measuring viscosity is a straight forward attempt to determine the behavior of both Newtonian and non-Newtonian materials in a number of simple flow situations using a suitable material function. This material function is termed "apparent viscosity," since it is a quanitity calculated from measurements in a particular instrument using a calibration or mathematical formula which is appropriate only to fluids of constant viscosity. The goal is to seek a correlation between material properties and observed behavior in practical situations. The behavior of flowing materials can be conveniently represented by means of flow curves. These are generated in a graph of shear stress versus shear rate, the so called rheogram. Rheograms contain increasing and decreasing shear rate flow curves unique to the material being tested. The advantage over one-point viscosity determination is that rheograms provide a complete picture of the materials' response to varying shear rates. These tests are best suited for: Industrial applications Process designing Determining processability End product performance Rheograms can supply direct information regarding yield stress, shearing history and thixotropy. They can also indirectly indicate dispersability, development of three dimensional structural netowrks and degree of flocculation (in wet state). Another interesting feature is the ability to determine the flocs' resistance to shearing. The cricial shear rate can be identified before material breakdown occurs.

n = Apparent Viscosity s = Geometrical Bob Factor (found on this chart) T = Torque in dynes-cm RPM = Rotation speed of the bob n = (9.55) (s) (T) / RPM

To confirm which RPM option was installed on your viscometer, locate the pulley on top of the spindle housing. If the pulley has 3 screws, your viscometer is set to go 6600 RPM. If the pulley has 2 screws, your viscometer is set to go 8800 RPM. In WinShear / WinShear32 under the SETTINGS menu, select MACHINE. If your viscometer is 6600 RPM, enter the spindle ration of 2. If your viscometer is 8800 RPM, enter the spindle ratio of 3.

The following USB to Serial Converter cables are the only ones that have been tested and approved by Kaltec Technicians: KeySpan - Model USA-19HS TRENDnet - Model TU-S9