Brookfield Falling Ball KF20 Instrukcja Użytkownika Pobierz pdf (Strona 15)

Brookeld Engineering Labs., Inc. Page 15 Manual No. M09-352-B0411

IV. DETERMINATION OF THE NON-NEWTONIAN BEHAVIOR

Non-Newtonian behavior can be determined when different measurement times are recorded

with repeated tests.

IV.1 Thixotrophy/Rheopexy

Thixotropy (rheopexy) is indicated if the travelling times for a ball decreases (increases) when

repeated measurements are made on the same volume of sample.

NOTE: If temperature control is not done correctly, thixotropy or rheopexy can be inferred

by mistake.

Rotational or Capillary Viscometers should be used for better determination of ow behavior.

IV.2 Structural Viscosity (Pseudoplasticity and Dilatancy)

Using the KF20 Falling Ball Viscometer at different angles may serve to determine pseudo-

plastic or dilatant behavior for non-Newtonian liquids. If the sample is non-Newtonian, the

travel time of the ball multiplied by the sine of the working angle for the KF20 will not remain

constant. This infers non-Newtonian ow behavior. For pseudoplasticity, the calculated value

decreases; for dilatancy, it increases.

NOTE: If temperature control is not done correctly, pseudoplasticity or dilatancy can be

inferred by mistake.

Details about the relative values for pseudoplasticity and dilatancy are related to the diameter

of the ball and the working angle.

More sophisticated equipment, like rotational viscometers/rheometers, should be used for de-

tailed examination of non-Newtonian materials.

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Brookfield Falling Ball KF20 Instrukcja Użytkownika Strona 15