Overview
EN ISO 1628-3:2010 - "Plastics - Determination of the viscosity of polymers in dilute solution using capillary viscometers - Part 3: Polyethylenes and polypropylenes" defines the particular conditions for measuring reduced viscosity (viscosity number/Staudinger function) and intrinsic viscosity (Staudinger index) of polyethylene and polypropylene. Tests are performed in dilute solution at 135 °C using capillary viscometers. The document notes that fillers or additives can affect measured values and may render results unreliable.
Key topics and technical requirements
- Test temperature: Measurements are carried out at 135 °C to ensure dissolution of ethylene polymers and isotactic polypropylene.
- Solvent: Decahydronaphthalene, analytical-reagent grade, redistilled (≤ 65 °C at ~500 Pa) and stabilized with 0.2% antioxidant to prevent oxidation during the test.
- Viscometer type: Preferably an Ubbelohde viscometer (type 0B or 0a) with a nominal viscometer constant 0.005, or equivalent capillary viscometers per ISO 3105. A modified Ubbelohde with an integrated filter is allowed when filtration is needed.
- Apparatus & conditions: Thermostatic bath maintained at 135 °C ±0.2 °C; secondary bath at 20 °C; precise timing (0.1 s resolution); analytical balance (0.1 mg); shaker in a 150 °C ±2 °C bath for dissolving.
- Procedure highlights: Measure efflux times of solvent and polymer solution; choose a solution concentration so that the ratio t_solution / t_solvent lies between 1.2 and 2.0; calculate reduced and intrinsic viscosity from efflux times and known concentration.
- Sample form: Test material must be dry powder or finely ground pieces; manufactured articles should be ground and homogenized to avoid surface/interior differences.
- Limitations: Presence of fillers, pigments or other additives can alter solution viscosity - report reliability caveats when such components are present.
Applications and users
- Quality control and batch verification in polyethylene (PE) and polypropylene (PP) production.
- R&D and polymer characterization for molecular weight estimation, processing behavior, and comparative material studies.
- Materials laboratories, certification bodies, and suppliers needing standardized intrinsic viscosity or viscosity number data for specifications and compliance.
- Useful for manufacturers of films, fibres, pipes, and molded products where polymer viscosity correlates with performance.
Related standards
- ISO 1628-1: General principles for dilute-solution viscosity measurements.
- Other parts of ISO 1628 (Parts 2, 4–6) for specific polymer groups.
- ISO 3105: Glass capillary kinematic viscometers - specifications and operation.
Keywords: EN ISO 1628-3:2010, viscosity of polymers, intrinsic viscosity, reduced viscosity, capillary viscometer, polyethylene, polypropylene, Ubbelohde viscometer, decahydronaphthalene, viscosity number.
