EN ISO 489:1999

1 Scope
2 Normative references
3 Apparatus and materials
  3.1 Method A
  3.2 Method B
4 Preparation of test specimens
  4.1 Method A
  4.2 Method B
  4.3 Required number of specimens or measurements
5 Conditioning
6 Procedure
  6.1 Method A
  6.2 Method B
7 Precision
8 Test report

This International Standard specifies two test methods for determining the refractive index of plastics, namely:Method A: a refractometric method for measuring the refractive index of moulded parts, cast or extruded sheetor film, by means of a refractometer. It is applicable not only to isotropic transparent, translucent, coloured oropaque materials but also to anisotropic materials. The method is recommended when great accuracy isrequired. It is not applicable to powdered or granulated material.Method B: an immersion method (making use of the Becke line phenomenon) for determining the refractiveindex of powdered or granulated transparent materials by means of a microscope. Monochromatic light should,in general, be used to avoid dispersion effects. The accuracy of this method is about the same as that ofmethod A. It is applicable to isotropic translucent, coloured materials but is not applicable to opaque materialsnor to anisotropic materials.NOTE 1 The refractive index is a fundamental property which can be used for checking purity and composition, for theidentification of materials and for the design of optical parts. The change in refractive index with temperature may give anindication of transition points of materials.NOTE 2 The accuracy of method B is approximately the same as that of method A when an experienced operator uses themethod with extreme care (see clause 7).