ISO 18553:2002

Overview

ISO 18553:2002 specifies a standardized laboratory method to assess the degree of pigment or carbon black dispersion in polyolefin pipes, fittings and compounds. The standard covers two specimen-preparation procedures (compression and microtome), microscopic examination, numerical grading of particle/agglomerate size and an optional visual appearance rating using photomicrographs. It applies to polyolefin products and pellets and specifically to carbon black–pigmented materials with carbon black content < 3%.

Key topics and technical requirements

• Scope: Assessment of pigment and carbon black particle/agglomerate size and dispersion in polyolefins; choice of procedure determined by the referring specification.
• Specimen preparation:
  • Compression procedure: cut six specimens (for pigment: 0.6 mg ± 0.2 mg; for carbon black: 0.20 mg ± 0.10 mg), heat between 150–210 °C and compress to films.
  • Microtome procedure: cut six slices of required thickness.
  • Target film thicknesses: pigment assessment 60 µm ± 20 µm; carbon black assessment 20 µm ± 10 µm; minimum 4 mm across.
• Microscopy:
  • Examine under transmitted light; recommended magnification ×100 for grading (≥×70 for appearance rating).
  • Ignore particles < 5 µm; measure largest dimension of each particle/agglomerate.
• Grading and reporting:
  • Use normative Table A.1 to assign size grades for each specimen; calculate arithmetic mean of six gradings and express to one decimal, rounded up.
  • Optional appearance rating by comparison with photomicrographs in Annex B.
  • Test report must identify material, preparation method, individual and average gradings, appearance rating (if required), deviations and test date.
• Normative/informative annexes:
  • Annex A: grading table (normative).
  • Annex B: photomicrographs for appearance evaluation (normative).
  • Annex C: grading examples (informative).
  • Annex D: basic specification guidance (informative) - recommended mean grading ≤ 3 and appearance not worse than micrograph B.

Practical applications and users

ISO 18553 is used by:

• Quality control and R&D laboratories testing polyolefin pipe and fitting compounds for uniform pigment/carbon black dispersion.
• Polymer compounders and pipe manufacturers to verify mixing, stabilizer distribution and UV-protection performance.
• Material suppliers and specifiers ensuring raw pellets meet dispersion requirements before extrusion or molding.
• Standards committees and test laboratories referencing a harmonized method for compliance and supplier acceptance.

Typical applications include production control for colored or carbon-black–stabilized pipes, troubleshooting dispersion-related defects, and validating compounding processes.

Related standards

• ISO 18553 consolidates and replaces ISO 11420:1996 (carbon black dispersion) and ISO 13949:1997 (pigment dispersion).
• Use alongside product-specific test methods and other ISO/TC 138 publications for plastics pipe systems.

Keywords: ISO 18553, pigment dispersion, carbon black dispersion, polyolefin pipes, fittings, compounds, microscopy, grading table, specimen preparation.