Overview
EN ISO 489:2022 (adoption of ISO 489:2022) specifies two standardized test methods for determining the refractive index of plastics. The document is intended for use across plastics testing labs, quality control, material identification and optical design. It supersedes the previous edition (EN ISO 489:1999) and is published under CEN/ISO collaboration.
- Methods covered:
- Method A - Refractometric method (Abbe or equivalent refractometer) for moulded parts, cast/extruded sheet or film, including isotropic and anisotropic materials.
- Method B - Immersion method (Becke line technique) using a microscope for powdered or granulated transparent plastics.
Key topics and technical requirements
- Apparatus
- Method A: Abbe refractometer (or equivalent) accurate to 0.001 in the refractive index range 1.300 to 1.700. Temperature control for prisms and specimen at (23 ± 0.5) °C.
- Method B: Microscope with at least 200× magnification (objective ≈ 20×) and a condenser allowing a narrow axial beam; monochromatic light (typically sodium D line, 589 nm) to minimise dispersion.
- Contacting / immersion liquids
- Liquids must have known refractive indices, not soften or dissolve the plastic, and be chosen to bracket the sample’s index. Examples listed include 1‑bromonaphthalene, methylene iodide (diiodomethane), various silicone oils and calibrated potassium mercury(II) iodide solutions. Users are warned about environmental and health hazards and must follow local regulations.
- Specimen preparation
- Sheet specimens recommended thickness 3–5 mm for Method A; measurement faces must be optically flat. Method B uses mounted particles with immersion liquids of known nD.
- Precision and reporting
- Precision information and interlaboratory data are provided (moved to Annex A in this edition). Test reports should record method, apparatus, temperature, contacting/immersion liquid, specimen details and results.
Applications and users
- Practical uses:
- Material identification and verification of composition or purity.
- Quality control of optical and non‑optical plastic parts (films, sheets, granules).
- Optical design and engineering-selection of plastics by refractive index for lenses, displays and light-guiding components.
- Monitoring temperature-dependent index changes to detect transition points.
- Typical users: plastics testing laboratories, OEMs in optics and lighting, materials scientists, polymer manufacturers and conformity assessment bodies.
Related standards
- ISO 291 (standard atmospheres for conditioning and testing) is normative in relation to specimen conditioning for EN ISO 489:2022.
Keywords: EN ISO 489:2022, ISO 489:2022, refractive index of plastics, refractometer, Abbe refractometer, immersion method, Becke line, optical properties, material identification, plastics testing.