Overview
ISO 13227:2025 specifies a laboratory test method for determining the flow point and other viscoelastic (rheological) properties of lubricating greases using an oscillatory rheometer with a parallel‑plate measuring system. The standard sets out sample preparation, instrument requirements, measurement programs, temperature control, evaluation and reporting procedures to ensure reproducible characterization of grease behaviour under oscillatory shear.
Key topics and technical requirements
- Scope: Determination of the flow point (τf) and additional viscoelastic parameters (storage modulus G', loss modulus G", loss factor tanδ) for lubricating greases; recommended for NLGI consistency grades 0 to 2.
- Apparatus: Air‑bearing oscillatory rheometer with a parallel‑plate system (25 mm plate diameter) and precise temperature control (±0.1 °C).
- Measuring gap and filling: Procedures for setting plate distance (initial 1,025 mm then trimmed to H = 1,000 mm as specified), degassing of samples, and trimming to avoid air bubbles. The gap should exceed 10× the largest solid particles in the sample.
- Measurement programs: Two measurement modes:
- Method A (amplitude/strain sweep): recommended γ range 0.01% to 1 000% with logarithmic increments.
- Method B (amplitude/stress sweep): recommended τ range 1 Pa to 10 000 Pa with logarithmic increments.
Constant angular frequency ω = 10 s⁻¹ (≈1.59 Hz) is recommended; results can be frequency‑dependent.
- Temperature control: Defined heating/cooling rates (0.4 °C/min), stabilization times (e.g., 15 min at 25 °C; 30 min at −40 °C), and precautions for low‑temperature testing (purge with dried gas to prevent ice).
- Evaluation and reporting: Use double‑logarithmic plots of τ vs G' and G" to determine flow and yield points; standard specifies precision (repeatability/reproducibility) and required test report elements.
Applications and users
ISO 13227:2025 is intended for:
- Lubricant manufacturers evaluating grease formulation, consistency and low‑temperature performance.
- Quality control laboratories performing routine rheological testing and acceptance checks.
- R&D teams developing grease chemistries, thickeners and additives where viscoelastic behaviour (flow point, yield behavior, G', G") is critical.
- Tribology and reliability engineers assessing grease suitability for bearings, automotive, aerospace, industrial and cold‑climate applications.
Keywords: ISO 13227:2025, lubricating greases, rheological properties, flow point, oscillatory rheometer, parallel‑plate, viscoelastic, storage modulus, loss modulus, tanδ, grease testing.
Related standards
- ISO 23572 - Petroleum products - Lubricating greases - Sampling of greases (referenced for sampling procedures).
- ISO 6743‑99 - (for NLGI consistency grading reference as noted in ISO 13227).