Brookfield DV2+Pro Viscometer Uživatelský manuál stáhnout pdf (Strana 25)

Brookeld Engineering Labs., Inc. Page 25 Manual No. M03-165-F0612

Please see our publication, “More Solutions to Sticky Problems”, for more detail relating to

sample preparation.

III.3 Selecting a Spindle/Speed

The DV-II+Pro has the capability of measuring viscosity over an extremely wide range. For

example,theRVDV-II+Procanmeasureuidswithintherangeof100-40,000,000cP.This

range is achieved through the use of several spindles over many speeds. See Appendix B for

details.

  Theprocessofselectingaspindleandspeedforanunknownuidisnormallytrialanderror. An

appropriate selection will result in measurements made between 10-100 on the instrument

% torque scale. Two general rules will help in the trial and error process.

1) Viscosity range is inversely proportional to the size of the spindle.

2) Viscosity range is inversely proportional to the rotational speed.

  Inotherwords:tomeasurehighviscosity,chooseasmallspindleand/oraslowspeed.Ifthe

chosen spindle/speed results in a reading above 100%, then reduce the speed or choose a smaller

spindle.

Experimentation may reveal that several spindle/speed combinations will produce satisfactory

results between 10-100%. When this circumstance occurs, any of the spindles may be selected.

  Non-Newtonianuidbehaviorcanresultinthemeasuredviscosityandyieldstresschangingif

the spindle and/or speed is changed. See our publication, “More Solutions to Sticky Problems,”

for more details.

When viscosity data must be compared, be sure to use the same test methodology: namely

the same instrument, spindle, speed, container, temperature and test time.

III.4 Multiple Data Points

The majority of viscosity and yield stress measurements are made at the quality control level

and often consist of a single data point. The test is conducted with one spindle at one speed.

The data point is a useful bench mark for the go/no-go decision in a production setting. The

DV-II+Pro can be used for single point measurement.

  Manyuidsexhibitacharacteristicchangeinviscosityandyieldstresswithachangeinapplied

force.Thisnon-Newtonianowbehavioriscommonlyseeninpaints,coatingsandfoodproducts

as a decrease in viscosity as shear rate increases or an increase in yield stress as a rotational speed

increases. This behavior cannot be detected or evaluated with the single point measurement.

  Non-Newtonianowisanalyzedthroughthecollectionofviscositydataoverarangeofshear

rates and the generation of a graph of viscosity versus shear rate (a rheogram). This information

willallowforamorecompletecharacterizationofauidandmayhelpinformulationand

production of a product. The DV-II+Pro is capable of collecting multiple data points for

comprehensiveanalysisofowbehavior.

  Moreinformationonowbehavior,shearrateandrheogramsisavailableinourpublication,

“More Solutions to Sticky Problems.”

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Brookfield DV2+Pro Viscometer Uživatelský manuál Strana 25