ISO 11443:2021

Overview

ISO 11443:2021 specifies standardized methods for determining the fluidity (rheological behavior) of plastic melts using capillary and slit‑die rheometers. The standard covers testing under shear rates and temperatures representative of plastics processing, accounts for shear‑rate and shear‑stress dependence of melt viscosity, and includes procedures to assess extrudate swelling. This fourth edition (2021) updates the technique set (including use of a zero‑length die) and provides requirements for apparatus, measurement, calibration and data reporting.

Key topics and technical requirements

• Test methods: Two principal geometries - capillary dies (Method A) and slit dies (Method B) - with procedures for volume flow‑controlled and pressure‑controlled measurements (Method 1 and Method 2).
• Measured quantities: Volume flow rate, apparent and true shear rate, apparent and true shear stress, and viscosity. Guidance is provided for converting apparent to true values (e.g., Bagley corrections for entrance/exit effects).
• Extrudate swelling: Procedures for measuring and reporting swell at room temperature and at test temperature.
• Apparatus and calibration: Detailed requirements for rheometer barrel, dies, piston, temperature control and measurement, pressure transducers and calibration, and volume‑flow measurement.
• Temperature and pressure control: Methods for selecting, measuring and calibrating test temperature and test pressure to reflect processing conditions.
• Material scope and limitations: Applies to thermoplastic melts (including those showing wall slip) and some thermosetting plastics; however, shear‑rate/viscosity derivations assume wall‑adhering behavior - the standard notes limitations for non‑wall‑adhering fluids.
• Data treatment and reporting: How to express results, corrections (Bagley, H/B geometry corrections), precision, and mandatory elements of the test report.

Practical applications

• Characterizing melt viscosity and flow behavior for process design and optimization (extrusion, injection molding).
• Comparing grades of polymers and additives for processability.
• Generating rheological input data for process simulation and quality control.
• Evaluating effects of temperature, shear rate and shear stress on melt behavior.
• Assessing extrudate swelling relevant to die design and dimensional control.

Who should use ISO 11443:2021

• Polymer rheologists and materials scientists
• Process engineers in extrusion and molding
• Quality control and R&D labs in plastics manufacturing
• Equipment manufacturers (rheometers, dies, sensors)
• Standards and regulatory professionals working with polymer processing data

Related standards

• ISO 1133‑1 / ISO 1133‑2 (MFR / MVR methods)
• ISO 4287 (surface texture)
• ISO 11403‑2 (data acquisition and presentation)
• ISO 6507‑1 (Vickers hardness - referenced for apparatus checks)

Keywords: ISO 11443, plastics rheology, capillary rheometer, slit‑die rheometer, melt viscosity, extrudate swelling, polymer processing, shear rate, shear stress.