Overview
ISO 2555:2018 specifies a standardized method to determine the apparent viscosity of plastics resins (including emulsions and dispersions) using a single cylinder type rotational viscometer. The method covers measurements from 0.02 Pa·s to 60 000 Pa·s, and is applicable to both Newtonian and non-Newtonian liquids. The apparent viscosity reported is dependent on the velocity gradient imposed during the measurement (non-constant shear rate inherent to single-cylinder instruments).
Key topics and technical requirements
- Scope and measurement range: Viscosity determination for resins in liquid form, emulsions or dispersions, 0.02–60 000 Pa·s.
- Measurement principle: A spindle (cylinder or disc) rotates at constant angular velocity; the fluid’s resistance produces a torque which is converted to apparent viscosity using spindle-specific calibration coefficients.
- Viscometer types: Allows both analogue (dial) and digital single-cylinder viscometers; digital devices automatically measure angle deviation and display viscosity when spindle and speed are entered.
- Models and spindles: Model categories L, R, H(A), H(B) (increasing maximum torque capacity), with interchangeable spindles (L1–L4, R1–R7) sized for different viscosity ranges.
- Test conditions: Guidance on choice of spindle and rotational speed, immersion level marks on spindles, use of guard stirrups (Annex B), thermostatic baths and additional apparatus to control temperature.
- Accuracy and calibration: Calibration method and accuracy considerations are included; measured values for non-Newtonian fluids are conditional on shear conditions and instrument model.
- Documentation: Required procedure steps, expression of results and test-report content are defined.
Practical applications
ISO 2555:2018 is used to obtain repeatable, comparable apparent viscosity data for:
- Quality control of liquid resins, coatings, adhesives, inks and polymer dispersions
- R&D and formulation optimization (processability, flow behavior)
- Production monitoring (batch consistency, viscosity-driven process adjustments)
- Incoming material inspection and supplier specification verification
Because the method uses a single-cylinder approach (non-constant shear), it is particularly suited for routine QC where simple, low-cost instruments (e.g., Brookfield-type viscometers) provide meaningful comparative viscosity values.
Who should use this standard
- Plastics and polymer manufacturers
- Formulators of emulsions, coatings and adhesives
- QC/QA laboratories and testing service providers
- R&D and process engineers responsible for flow properties and product consistency
Related standards
- ISO 3219 - methods using coaxial cylinder and cone-plate rotational rheometers (constant shear-rate techniques)
- ISO 1652 - terminology and related terms referenced in the introduction
Keywords: ISO 2555:2018, single cylinder type rotational viscometer, apparent viscosity, plastics resins, viscosity measurement, Newtonian, non-Newtonian, Brookfield, spindle, rotational speed.
Open preview (PDF)Plastics — Resins in the liquid state or as emulsions or dispersions — Determination of apparent viscosity using a single cylinder type rotational viscometer method
