This Standard specifies two test methods for determining the refractive index of plas-
tics, namely:
-- Method A: a refractemetric method for measuring the refractive index of moulded
parts, cast or extruded sheet or film, by means ofa refractometer. It is applicable
not only to isotropic transparent, translucent, coloured or opaque materials but also
to anisotropic materials. The method is recommended when great accuracy is re-
quired. It is not applicable to powdered or granulated material.
-- Method B: an immersion method (making use of the Becke line phenomenon) for
determining the refractive index 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 of
method A. It is applicable to isotropic translucent, coloured materials but is not
applicable to opaque materials nor to anisotropic materials.
NOTE 1 The refractive index is a fundamental property which can be used for
checking purity and composition, for the identification of materials and
for the design of optical parts. The change in refractive index with tem-
perature may give an indication 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 the method with extreme care.
NOTE 3 The International Standard corresponding to this Standard is as follows.
ISO 489:1999 Plastics-Determination of refractive index (MOD)
In addition, symbols which denote the degree of correspondence in the
contents between the relevant International Standard and JIS are IDT
(identical), MOD (modified), and NEQ (not equivalent) according to I80/
IEC Guide 21.