Overview - EN ISO 2555:2018 (Plastics resins - apparent viscosity)
EN ISO 2555:2018 specifies a standardized laboratory method to determine the apparent viscosity of plastics resins (liquids, emulsions or dispersions) using a single cylinder type rotational viscometer. The method covers viscosity measurements from 0.02 Pa·s to 60 000 Pa·s and applies to both Newtonian and non‑Newtonian systems. The measured value is an apparent viscosity because it depends on the spindle, rotational speed and the velocity gradient (shear rate) imposed during the test.
Key topics and technical requirements
- Measurement principle: a rotationally symmetric spindle (cylinder or disc) is driven at constant angular velocity; fluid resistance produces a torque that is converted to an apparent viscosity using spindle- and speed-dependent coefficients.
- Apparatus: single cylinder type rotational viscometers (analogue/dial and digital types are permitted), thermostatic baths and auxiliary equipment as required.
- Spindles and speeds: guidance for selection of spindle geometry and rotational speed to cover the viscosity range and sample types.
- Applicability: valid for both Newtonian and non‑Newtonian resins; results vary with shear conditions and must be reported accordingly.
- Calibration and accuracy: the 2018 revision adds calibration instructions and accuracy considerations; calibration tables or device settings are used to convert torque to apparent viscosity.
- Reporting: format and minimum content for test reports (test conditions, spindle, speed, temperature, measured apparent viscosity) are defined.
- Supporting annexes: Annex A offers recommended test conditions for general resin testing; Annex B defines spindle and guard stirrup details.
Practical applications and users
EN ISO 2555:2018 is used where consistent, comparable viscosity data are needed for:
- Quality control and batch release of polymer resins, adhesives, coatings and emulsions
- R&D and formulation optimization (polymers, paints, inks, sealants)
- Incoming material inspection and suppliers’ specifications
- Process control where viscosity affects mixing, pumping or coating performance
Typical users:
- Polymer and chemical manufacturers
- QC and analytical laboratories
- Formulation scientists and process engineers
- Test laboratories performing contract materials testing
Related standards
- ISO 3219 - rotational viscometry (coaxial cylinder and cone‑plate methods) - relevant when constant shear‑rate methods are required
- ISO 1652 - terminology and related terms referenced in the standard
- Historical method reference: Brookfield technique - background to single cylinder rotational viscometry
EN ISO 2555:2018 provides a practical, widely accepted procedure for obtaining comparative viscosity data of plastics resins using single-cylinder rotational viscometers. Use it to ensure repeatable test conditions, correct spindle/speed selection, and standardized reporting for regulatory, QA and R&D workflows.
