ISO 18553:2025

Overview

ISO 18553:2025 specifies a laboratory method for assessing the degree of pigment or carbon black dispersion in polyolefin pipes, fittings and compound raw materials. The standard defines two preparation procedures - a microtome procedure (primary) and an optional compression procedure - and provides objective particle/agglomerate size grading and a photographic reference system for appearance rating. It applies to polyolefin products and pellets containing up to 3% carbon black or 5% pigment by weight.

Key Topics and requirements

• Scope and applicability
  • Applies to polyolefin pipes, fittings and pellet compounds; choice of procedure is determined by the referring specification.
  • Limits: carbon black < 3% wt; pigments < 5% wt.
• Principle
  • Produce thin test slices (microtome) or heat-and-compress specimens, then examine microscopically.
  • Measure particle and agglomerate sizes and assign arithmetic gradings from multiple test pieces.
• Test-piece preparation
  • Microtome slices are preferred for product and raw-material testing; compression method is allowed for some raw materials but may alter agglomerate morphology.
  • Example slice thicknesses given: (20 ± 5) µm for black materials; (40 ± 10) µm for pigmented materials.
  • Six test pieces are prepared and evaluated to derive an average grading.
• Microscopy and measurement
  • Use an optical microscope (or digital imaging system) with calibrated graticule or stage micrometer.
  • Lighting and magnification should allow identification of defined size ranges; measurements are compared to tabulated grading (Annex A).
  • Photomicrographs (Annex B) are provided for appearance rating and comparison.
• Reporting
  • Results expressed as particle/agglomerate size grading and optional appearance rating. Test report content and examples are specified.

Practical applications

• Quality control and production acceptance for manufacturers of polyolefin pipes and fittings.
• Raw-material qualification for compounders and black/pigment suppliers.
• Incoming inspection and supplier verification in supply chains where dispersion affects mechanical properties, UV protection and product appearance.
• R&D and failure analysis to correlate dispersion quality with performance (surface finish, strength, UV stability).

Who uses this standard

• Pipe and fitting manufacturers, compounders, testing laboratories, regulatory bodies, and purchasers specifying dispersion limits in procurement or product standards.

Related standards

• ISO 293 (compression moulding of thermoplastic test specimens)
• ISO 1133-1 (melt mass-flow rate / MFR test) - referenced as alternate sample generation method

Keywords: ISO 18553:2025, pigment dispersion, carbon black dispersion, polyolefin pipes, microtome procedure, compression procedure, particle size grading, photomicrographs.