ISO 6721-10:2015

Overview

ISO 6721-10:2015 - Plastics - Determination of dynamic mechanical properties - Part 10: Complex shear viscosity using a parallel-plate oscillatory rheometer - defines a standardized method to measure the dynamic rheological behavior of polymer melts using a parallel-plate oscillatory rheometer. The method covers determination of complex shear viscosity (η*), its real and imaginary parts (η′, η″), complex shear modulus (G*), shear storage modulus (G′) and shear loss modulus (G″), typically over angular frequencies from 0.01 rad·s⁻¹ to 100 rad·s⁻¹ and for complex shear viscosity values up to around ~10 MPa·s.

Key topics and technical requirements

• Test principle: Specimen placed between concentric, circular parallel plates; oscillatory excitation in either controlled-strain or controlled-stress mode; measure torque, angular displacement and phase shift to compute η* and G*.
• Frequency & temperature sweeps: Guidance on frequency sweeps, temperature control and limitations (low-frequency tests can be long; high frequencies can cause edge fracture).
• Apparatus specifications: Parallel-plate geometry (typical plate diameters 20–50 mm); plate surface finish Ra ≤ 0.25 µm; plate separation (specimen thickness) recommended 0.5–3 mm with D/d ratio ~10–50 to minimize error.
• Accuracy & calibration: Instrument must measure torque reliably (apparatus capable of ±2 % of the minimum torque amplitude used) and angular frequency within ±2 %. Temperature control and measurement resolution requirements (e.g., ±0.5 °C up to 200 °C; ±1.0 °C for 200–300 °C; ±1.5 °C above 300 °C).
• Specimen handling & test procedure: Zeroing the gap, conditioning, determination of linear viscoelastic region, thermal stability checks, and mitigation of air entrapment.
• Validation & verification: Annexes provide guidance on uncertainty limits and rheometer performance verification.

Applications and users

This standard is essential for:

• Polymer rheologists and material scientists performing melt rheology characterization.
• Quality control and contract testing laboratories evaluating processability, flow behavior and viscoelastic properties.
• R&D teams in plastics, adhesives, composites and polymer processing (extrusion, injection moulding) seeking reliable, comparable viscosity and modulus data.
• Material suppliers and formulators who need standardized data for datasheets and process design.

Practical uses include melt-flow characterization, formulation optimization, process simulation input, and comparison of polymer grades under controlled dynamic shear conditions.

Related standards

• ISO 6721-1: General principles for dynamic mechanical properties of plastics
• Other parts of ISO 6721 (Parts 2–12) covering torsion, flexural, tensile and other dynamic test methods
• ISO 472: Plastics - Vocabulary
• ISO 5725-1: Accuracy (trueness and precision) of measurement methods and results

Keywords: ISO 6721-10:2015, complex shear viscosity, oscillatory rheometer, parallel-plate, polymer melts, dynamic rheological properties, G′, G″, η*, rheology standard.