Overview
ISO/TS 289-4:2017 defines a standardized method to determine the Mooney stress-relaxation rate (MSR) of uncompounded or compounded, unvulcanized rubber using a shearing-disc viscometer. The MSR quantifies the elastic (stress-relaxation) response of rubber immediately after stopping the Mooney rotor and complements the conventional Mooney viscosity measurement. The document is intended primarily for quality control use.
Key topics and technical requirements
- Scope: Measurement of MSR for unvulcanized rubbers to characterize elastic behaviour in addition to viscosity.
- Apparatus and calibration:
- Use a shearing-disc viscometer conforming to ISO 289-1; follow the calibration schedule in Annex B.
- The viscometer must stop the rotor within 0.1 s, reset zero torque to static zero, and record torque at least every 0.2 s after stopping.
- Test procedure:
- Perform a standard Mooney viscosity test per ISO 289-1; then abruptly stop the rotor and record torque decay.
- Collect relaxation data from 1.6 s to 5.0 s after rotor stop (typically ~18 data points).
- Automatic data acquisition is recommended for repeatability.
- Data analysis:
- Fit a power-law model T = k t^(-α) (log T vs log t) over the specified short interval.
- The MSR is the absolute value of the slope (α) of the linear regression on the log-log plot, reported to the nearest third decimal.
- Report the standard error from the regression as an estimate of random error.
- Reporting:
- Include viscometer make/model, reference ISO/TS 289-4, any deviations from the prescribed interval, MSR (to three decimals) and its standard error, plus the associated Mooney viscosity.
- Precision and annexes:
- Precision data are provided in Annex A; calibration schedule in Annex B.
Applications and users
- Practical for quality control laboratories in rubber manufacturing to detect changes in elastic behaviour that Mooney viscosity alone may not reveal.
- Valuable to rubber technologists, compounders, polymer researchers, and viscometer manufacturers for:
- Monitoring batch-to-batch consistency.
- Differentiating polymer grades (e.g., high molecular weight fractions).
- Verifying equipment performance and inter-lab comparability (note sensitivity to motor stopping characteristics).
Related standards
- ISO 289-1:2015 - Determination of Mooney viscosity (shearing-disc viscometer).
- ISO 18899:2013 - Guide to calibration of test equipment.
- ISO/TS 289-4 is part of the wider ISO 289 series covering rheological determinations on unvulcanized rubber.
Keywords: ISO/TS 289-4:2017, Mooney stress-relaxation rate, MSR, shearing-disc viscometer, Mooney viscosity, unvulcanized rubber, quality control.