ISO 6721-10:2025

Overview

ISO 6721-10:2025 - Plastics: Determination of dynamic mechanical properties, Part 10 - specifies a standardized method for measuring complex shear viscosity and related dynamic rheological properties of polymer melts using an oscillatory rheometer with either parallel‑plate or cone‑and‑plate geometry. The method covers angular frequencies typically from 0.01 rad·s‑1 to 100 rad·s‑1 (other frequencies may be used) and is suitable for complex shear viscosity values typically up to about 10 MPa·s. Measured parameters include η* (complex shear viscosity), η' (dynamic shear viscosity), η" (out‑of‑phase viscosity), G* (complex shear modulus), G' (storage modulus), G" (loss modulus), phase angle δ and tanδ.

Key topics and requirements

• Measurement geometries: detailed descriptions and requirements for parallel‑plate and cone‑and‑plate fixtures.
• Test modes: defined controlled‑strain (sinusoidal displacement) and controlled‑stress (sinusoidal torque) operation and when to use each.
• Instrument performance: requirements for measuring torque, angular displacement and angular frequency (e.g., torque accuracy within ±2 % and angular frequency within ±2 %).
• Temperature control: guidance on enclosures, inert atmospheres for oxidation‑sensitive samples and temperature measurement accuracy (±0.5 °C up to 200 °C; ±1.0 °C for 200–300 °C; ±1.5 °C above 300 °C).
• Test procedure: specimen sampling and placement, gap zeroing, conditioning, determination of thermal stability and the linear‑viscoelastic region, frequency and temperature sweeps, and air‑entrapment checks.
• Data and calculations: expression of results, calculation of G*, η*, phase angle and loss factor; assumptions of linear‑viscoelastic behaviour.
• Quality and verification: calibration, performance verification, precision, uncertainty limits and required test reporting (see annexes on uncertainty and rheometer verification).

Applications and who uses it

ISO 6721-10:2025 is used by:

• Polymer rheologists and researchers for characterizing melt viscoelasticity.
• Quality control and product development labs to monitor processing‑relevant viscosity and viscoelastic behaviour.
• Materials suppliers and compounders to specify melt properties for extrusion, injection molding and film processes.
• Rheometer manufacturers and calibration laboratories for performance checks and compliance testing. Practical applications include optimizing processing conditions, comparing materials, validating rheological models and ensuring reproducible material specifications.

Related standards

• ISO 6721‑1 - General principles for determination of dynamic mechanical properties
• ISO 472 - Plastics vocabulary
• ISO 5725‑1 - Accuracy (trueness and precision) of measurement methods and results

Keywords: ISO 6721-10:2025, complex shear viscosity, oscillatory rheometer, parallel‑plate, cone‑and‑plate, polymer melts, dynamic shear viscosity, storage modulus, loss modulus, frequency sweep, temperature control.