Overview
EN ISO 8780-3:1995 (identical to ISO 8780-3:1990) defines a laboratory method for dispersing pigments and extenders using a high-speed impeller mill to assess their dispersion characteristics. The procedure is intended for mill bases of moderately high viscosity (high binder and/or pigment concentration producing high shear). It is designed to be used with the assessment methods in ISO 8781 and requires agreed supplementary information (Annex A) for specific applications. This part is for laboratory evaluation and is not a direct recipe for scaling to full production mills.
Key topics and technical requirements
- Scope: Dispersion using a horizontal disc (impeller) mill; suitable for pre-dispersing or partially dispersing pigments prior to further milling.
- Apparatus: High-speed impeller mill with a disc (often serrated) and motor drive; adjustable height and clamping for concentric alignment; optional temperature control (double-walled vessel).
- Vessel/disc geometry: Specified relative dimensions (disc diameter d):
- Vessel diameter: ~1.3 d to 3 d
- Clearance between disc plane and vessel base: ~0.25 d to 0.5 d
- Mill base depth: ~0.5 d to 2 d
- Operating speed: Peripheral disc speed adjustable in the laboratory range (typically 5 m/s to 20 m/s); disc type, vessel geometry and speed must be agreed and recorded.
- Mill base: High-viscosity mill base needed to create a toroidal flow; pigment and binder concentrations chosen by prior experiment to produce the correct flow pattern.
- Procedure highlights:
- Sampling per ISO 842
- Pre-mixing at reduced speed to wet pigment (~5 min), incorporating pigment so some remains visible
- Dispersion at agreed speed with test portions taken at agreed stirring times (examples: 4, 8, 16, 32 min)
- Stabilization and de-aeration procedures as required and agreed
- Reporting: Must include product ID, reference to the standard, supplementary information from Annex A, any deviations and test dates.
Applications and users
- Primary users: Pigment and extender manufacturers, paint and coatings formulators, R&D labs, quality control and materials testing laboratories.
- Practical uses:
- Compare dispersibility and performance of pigments in a standardized laboratory mill
- Pre-disperse samples before bead-milling or attritor processing
- Evaluate effects of binder systems, pigment loading, and formulation on tinting strength, grind fineness, and gloss (used in conjunction with ISO 8781 test methods)
- Establish repeatable laboratory procedures for QA and R&D comparisons
- Benefits: Reproducible small-batch testing, controlled shear conditions, objective comparison of pigment dispersibility.
Related standards
- ISO 8780-1 (Introduction)
- ISO 8780 parts 2, 4, 5, 6 (other dispersion equipment: oscillatory shaker, bead mill, muller, triple-roll mill)
- ISO 8781 series (methods of assessment: tinting strength, fineness of grind, gloss)
- ISO 842 (sampling of raw materials)
Keywords: EN ISO 8780-3:1995, ISO 8780-3, high-speed impeller mill, pigments and extenders, dispersion characteristics, mill base, binder system, pigment dispersibility, laboratory dispersion testing.