Plastics — Determination of refractive index
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 sheet
or film, by means of a 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
required. 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 temperature 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 (see clause 7).
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Methods of testing plastic, Introduction
BS 2782-1:Method 140A:1992
Methods of testing plastics. Thermal properties, Determination of the burning behaviour of horizontal and vertical specimens in contact with a small-flame ignition source
BS 2782-1:Method 140E:1982
Methods of testing plastics. Thermal properties, Flammability of a small, inclined test piece exposed to an alcohol flame (laboratory method)
BS 2782-1:Method 150D:1976
Methods of testing plastics. Thermal properties, Cold crack temperature of film and thin sheeting