ISO 23900-3:2015

Overview

ISO 23900-3:2015 - "Pigments and extenders - Methods of dispersion and assessment of dispersibility in plastics - Part 3" - specifies a laboratory method for assessing the colouristic properties and ease of dispersion of black and coloured pigments in polyethylene (PE) using a two-roll mill. The standard quantifies dispersibility as DH_PE, the percentage increase in colour strength achieved when pigments are further milled at a narrower roll gap. Photometric measurement and colour strength calculations follow ISO 18314-1 and ISO 787-24.

Key topics and requirements

• Scope and purpose
  • Measures colouristic properties of a test pigment relative to a standard and evaluates ease of dispersion (DH_PE) in polyethylene.
  • Two complementary procedures: Method A (powders and flakes, e.g., organic pigments, carbon black, many inorganic powders) and Method B (granules and masterbatches, suitable for inorganic pigments in any form).
• Sample preparation
  • Typical pre-blend: 100 parts PE + 1.0 part TiO2 (or 5.0 parts for carbon black) plus specified test pigment additions; antioxidant optional for HDPE.
• Dispersion procedure (two-roll milling)
  • Two-roll mill with roll diameter 80–200 mm; peripheral speed ratio ≈ 1:1.1.
  • Initial milling to form sheet at 0.4–0.5 mm gap (140–160 °C typical), cutting and folding every 30 s for a defined number of roll revolutions.
  • Further milling at reduced gap (0.3 mm) to evaluate improved dispersion.
• Specimen handling and measurement
  • Press sheets between high-gloss chrome steel plates (spacer ~1 mm) at up to 160–170 °C, cool rapidly.
  • Measure colour strength and colourimetric properties with photometer per ISO 18314-1; compute DH_PE as percentage increase in colour strength (0.3 mm vs 0.5 mm).
• Precision and reporting
  • Test report must identify product, method, materials, mill conditions, and measured DH_PE. Results are valid for the specified equipment and conditions.

Applications and users

• Useful for pigment manufacturers, additive suppliers, plastics compounders, and quality control / testing laboratories to:
  • Compare dispersibility of pigments in PE formulations.
  • Optimize pigment form (powder vs granule vs masterbatch) and processing conditions.
  • Support product specifications, troubleshooting dispersion-related defects (mottling, poor colour strength), and R&D screening.
• Particularly relevant where pigment reagglomeration or handling form influences dispersion (e.g., carbon black, organic powders).

Related standards

• ISO 23900 series (Parts 1, 2, 4–6) for broader dispersion assessment methods in plastics.
• ISO 18314-1 (analytical colorimetry) and ISO 787-24 (tinting strength / photometric methods) referenced for measurement and calculation.

Keywords: ISO 23900-3:2015, pigments, dispersibility, polyethylene, two-roll milling, colouristic properties, ease of dispersion, DH_PE.