March 20, 2023 By Rheometer Spares Off

Viscometer vs. Rheometer: Understanding the Differences

Looking to understand the key differences between a viscometer and a rheometer? Discover the unique features and benefits of each instrument to determine which one is the right fit for your specific rubber testing needs.

Viscometers and rheometers are used throughout the polymer industry to determine material properties before, during and after the vulcanisation process. The most commonly used versions in the rubber industry are a Mooney Viscometer and Rotational (Moving Die) Rheometer. Both apply a shearing force to a polymer sample within a sealed cavity. The reactionary torque of the sample is measured by a transducer and used to determine material properties. Test time, frequency, amplitude and temperature can all be varied to investigate more advanced material characteristics. 

Application Of Shearing Forces

The main difference lies in how the shearing force is applied and how the resultant torque is interpreted.

A Mooney Viscometer uses a rotor embedded within a sample to exert a shearing force by full rotation. Testing is typically at sub-cure temperatures. The resultant torque measurement is used to determine viscosity using an arbitrary scale, Mooney Units (MU). Conversely, a Rotational (Moving Die) Rheometer does not use a rotor, but instead utilises an oscillating die to exert a shearing force on a sample. Temperatures are typically higher, as to induce vulcanisation. The torque signal (dNm) is used to express both cure and rheological/viscoelastic properties.

Uses Of The Mooney Viscometer

The Mooney Viscometer is the industry standard test for pre-vulcanisation properties and has long been synonymous with the rubber industry. Typically, Mooney Viscosity (MU) is used as a yardstick the gauge the quality of raw materials, especially in grading natural rubber. Although Mooney Units use an arbitrary scale, results can be correlated empirically to other instruments. In particular, Scorch Time can be used as an indirect measure for cure onset properties. 

Uses Of The Moving Die Rheometer

The Moving Die Rheometer (MDR) is used extensively throughout the rubber industry to measure the curing properties of any compound at a given temperature. The cure properties can be used for compound formula optimisation and to perform inter- and intra-batch quality control. Providing a snapshot of how and when vulcanisation occurs, the MDR cure curves are an invaluable resource to rubber technologists who need to take account of both pre- and post-cure processing effects during any production line.

Viscometer vs. Rheometer Comparison Table

Mooney ViscometerRotational Rheometer
ModelMooney Viscometer
Mini Mooney Viscometer
*Mooney Viscometer Variable Speed
Moving Die Rheometer
Mini Moving Die Rheometer
**Multi-Function Rheometer
Primary MeasurementMooney ViscosityCure Properties
Rheological Properties
Viscoelastic Properties
Vulcanisation Uncured PolymerCured Polymer
AutomationNot AvailableAvailable
Die AssemblySealed Cavity; Large or Small RotorSealed Bi-Conical Cavity; Rotor-Less
MovementFull RotationOscillation
Frequency2 RPM (Std.)
*Up to 20 RPM
1.67 Hz
**Up to 50Hz
Amplituden/a0.5° (Std), 1.0°, 3.0°
**Up to 360°
Shearing ActionRotorMoving Die
Torque MeasurementMooney Units (MU)Torque (dNm)
Typical Test Temperature100°C180°C
Typical Sample Volume14.3 cm³4.5 cm³
StandardISO No. 289 / ASTM D1646ISO No. 6502 / ASTM D5289


Rheometers and viscometers both use the principles of rheological flow to measure the viscosity of a fluid under a shearing force. Although both instruments have a lot in common in principle, the application of shearing forces, test conditions and sample size differentiate the rheometer and viscometer within the rubber industry.

While the Mooney Viscometer can be used to measure pre-vulcanisation properties and gauge the quality of a material, the Moving Die Rheometer primarily provides cure curves that can be used to assess and modify both the rubber compounding formulation and process.

Often used together but equally strong independently, the Mooney Viscometer and Moving Die Rheometer comprehensively measure the primary properties of rubber, making them both key pieces of equipment for any rubber laboratory or production facility. 

Further Resources

For more information on the Mooney Viscometer and Moving Die Rheometer, visit the Prescott Instruments website to see the full instrument specification, plus additional modules and software options:

>> Mooneyline Mooney Viscometer

>> Rheoline Moving Die Rheometer

>> All viscometers

>> All rheometers

For parts, spares and consumables, follow the links below to head to the Rheometer Spares shop:

>> Mooney Viscometer parts & spares

>> Moving Die Rheometer parts & spares

>> All testing

>> All maintenance

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