Bareiss Prüfgerätebau GmbH

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Oscillation. Rotation. Process Analyzation.

The new RPA ultra.


Always on the move.

The RPA ultra combines highly dynamic measurement methodology with maximum rigidity.

Infinite possibilities.

With a fully rotational lower die, the RPA ultra achieves shear rates at unprecedented levels.

Down to the smallest detail.

The high sampling rate of the RPA ultra reveals hidden material characteristics.


Highest quality is our drive, customer-oriented solutions are our motivation:
that is why we, as a test equipment manufacturer, are expanding our product portfolio
and traditionally focus on innovation. With the new RPA ultra, materials can be inspected
like never before.

This new type of advanced RPA testing allows access to valuable information contained
in higher harmonics, steady shear viscosity or non-elliptical Lissajous figures.
The rotating lower chamber allows to determine the steady shear viscosity of materials for
the first time in spheres that are highly relevant to production.

This shifts the quality of testing to an unrivaled level.

Dive into new dimensions.

Fourier Transform Rheology

For detailed information please click the icons.

For an optimal signal-to-noise ratio during a measurement, the number of data points is of great importance. The RPAultra meets all requirements here: high sampling rate and instrument stiffness, state-of-the-art electronics and an optimized Fourier algorithm delivers unique results for material characterization.

The Fourier spectrum of the torque (modulus) and strain (displacement) is always analyzed and displayed; only then can material differences be made transparent in a repeatable manner.


To avoid distortion, the sampling frequency must be at least twice as high as the highest frequency you want to capture.


If the sampling is too low, the signal cannot be detected cleanly and the signal-to-noise ratio (SNR) decreases. This means that the higher harmonics are no longer clearly detectable.


Due to the extremely high sampling rate, higher harmonics can be easily measured with incomparable reproducibility.




Steady Shear Viscosity

To better understand the manufacturing process of an unvulcanized rubber compound, the steady shear viscosity is one of the most important properties, especially crucial for determining the process parameters for extrusion and injection molding purposes. The RPA ultra's rotating lower die with unlimited strain thus provides the user with a dual test mode: dynamic and steady shear.

Wall Slip

A significant challenge in the processing of rubber compounds is the issue of Wall Slip.

This is a rheological phenomenon where slippage occurs, for example, between the extruder wall and the flowing material. We offer an optional solution where the upper die is replaced by a defined polished die set. In combination with a programmable internal pressure, this allows Wall Slip experiments to be carried out.

Isothermal Test

One of the most common and important tests performed on rubber compounds are the isothermal cure tests.

All important test parameters such as maximum and minimum torque, TC values, reaction time and rate, etc. are determined and made available to the user in tabular or/and graphical form for further analysis in the BareissOne software.

Non-Isothermal Test

In order to evaluate the behavior of a sample over a wide temperature range, non-isothermal measurements (temperature sweep) are typically performed at different heating rates. This measurement at different heating rates also paves the way for kinetic calculations - a module that is also integrated into the BareissOne software.


From an isothermal test, values such as incubation time, reaction order and conversion rate constant can be determined for each temperature. The calculation is according to the DIN 53529 standard. With the help of the incubation time and the conversion rate constant at at least 3 different temperatures, the activation energies of the incubation and the conversion can also be determined. These are essential parameters for the computation of the heating time for the test specimen and also finds its use in production line.

Frequency Sweep

By characterizing a sample over a wide range of frequencies, the user obtains a comprehensive overview of the viscoelastic behavior as well as the molecular structure (molecular weight and molecular weight distribution).

Viscoelastic properties such as complex modulus, elastic modulus, loss modulus, complex viscosity, phase angle, etc. are calculated at each frequency as a result of the frequency-dependent behavior of the sample.

Strain Sweep

Measuring a specimen over a wide strain range shows the strain-dependent behavior, e.g., the linear viscoelastic range (LVE) up to Large Amplitude Oscillatory Shear (LAOS). The Payne test, which is performed at small strain amplitudes to investigate the (filler/polymer) filler networks, reveals information about the filler content and the filler dispersion levels.

Large Amplitude Oscillatory Shear (LAOS)

LAOS is essentially a strain sweep performed at relatively large amplitudes to investigate and evaluate the nonlinear viscoelastic behavior of a sample.

The nonlinear behavior of a material is based on its polymer architecture --> linear or branched polymer.

The LAOS results are also used for FT- Rheology. The calculation of the LCB index (Long Chain Branching) or the Q parameter is performed using the harmonic spectrum from Fourier analysis (FFT).


In the frequency and strain sweeps described above, one parameter (frequency or strain) is held constant while the other parameter (frequency or strain) is changed over a range. Matrix testing allows the user to change both parameters - frequency and strain - during a sweep, making the test method more flexible and thus providing more information with a single measurement.


„The RPA ultra expands the scope of application to better describe current topics in rubber technology, such as Wall Slip, Polymer Architecture and use of sustainable Fillers like recovered Carbon Black (rCB)“


„For more information, use our download service.“


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