ASTM D542-00
(Test Method)Standard Test Method for Index of Refraction of Transparent Organic Plastics
Standard Test Method for Index of Refraction of Transparent Organic Plastics
SCOPE
1.1 This test method covers a procedure for measuring the index of refraction of transparent organic plastic materials.
1.2 A refractometer method is presented. This procedure will satisfactorily cover the range of refractive indices found for such materials. Refractive index measurements require optically homogeneous specimens of uniform refractive index.
Note 1--This test method and ISO 489 are technically equivalent.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation:D542–00
Standard Test Method for
Index of Refraction of Transparent Organic Plastics
This standard is issued under the fixed designation D 542; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope * 3.1.2 dispersion—variation of refractive index with wave
length of light. C 162, C14
1.1 This test method covers a procedure for measuring the
3.1.3 index of refraction, n—thenumericalexpressionofthe
index of refraction of transparent organic plastic materials.
ratio of the velocity of light in a vacuum to the velocity of light
1.2 A refractometer method is presented. This procedure
in a substance at a specified wavelength. E 284, E12
will satisfactorily cover the range of refractive indices found
for such materials. Refractive index measurements require
4. Significance and Use
optically homogeneous specimens of uniform refractive index.
4.1 This test method measures a fundamental property of
NOTE 1—This test method and ISO 489 are technically equivalent.
matterwhichisusefulforthecontrolofpurityandcomposition
1.3 This standard does not purport to address all of the for simple identification purposes, and for optical parts design.
This test method is capable of readability to four figures to the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro- right of the decimal point.
priate safety and health practices and determine the applica-
5. Apparatus
bility of regulatory limitations prior to use.
5.1 The apparatus for this test method shall consist of an
2. Referenced Documents
Abbe’ refractometer (Note 2), a suitable source of white light,
2.1 ASTM Standards: and a small quantity of a suitable contacting liquid (Note 2 and
Note 3).
C 162 Terminology of Glass and Glass Products
D 618 Practice for Conditioning Plastics for Testing
NOTE 2—Other suitable refractometers can be used with appropriate
D 883 Terminology Relating to Plastics
modification to this procedure as described in Section 7.
D 1898 Practice for Sampling of Plastics
NOTE 3—Asatisfactorycontactingliquidisonewhichwillnotsoftenor
E 284 Terminology of Appearance otherwiseattackthesurfaceoftheplasticwithinaperiodof2hofcontact.
The index of refraction of the liquid must be higher, but not less than one
E 691 Practice for Conducting an Interlaboratory Study to
5 unit in the second decimal place, than the index of the plastic being
Determine the Precision of a Test Method
measured; for example, n of the sample = 1.500, n of the contacting
d d
2.2 ISO Standard:
liquid$1.510.
ISO 489-1983 Determination of the Refractive Index of
Transparent Plastics—Part A
6. Sampling
6.1 Samples shall be in accordance with the pertinent
3. Terminology
considerations outlined in Practice D 1898.
3.1 Definitions:
6.2 Samples may be drawn from any materials presentation
3.1.1 For definions of terms used in this test method, see
(for example, pellets, film, sheet, fabricated articles, etc.)
Terminologies D 883 and E 284.
which permits preparation of a satisfactory specimen as de-
scribed herein.
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
7. Test Specimens
and is the direct responsibility of Subcommittee D20.40 on Optical Properties.
Current edition approved Nov. 10, 2000. Published January 2001. Originally
7.1 The test specimen shall be of a size that will conve-
published as D 542 – 39. Last previous edition D 542 – 95.
niently fit on the face of the fixed half of the refractometer
Annual Book of ASTM Standards, Vol 15.02.
prisms (Note 4).Aspecimen measuring 6.3 by 12.7 mm on one
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 06.01.
face is usually satisfactory.
Annual Book of ASTM Standards, Vol 14.02.
NOTE 4—For maximum accuracy in the refractometer method, the
Available from American National Standards Institute, 11 W. 42nd St., 13th
Floor, New York, NY 10036. surface contacting the prism must be flat. This surface can be judged for
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D542
flatness, provided the specimen has been satisfactorily polished, by
10. Report
observing the sharpness of the dividing line between the light and dark
10.1 Report the following information:
field as viewed in the ocular. A sharply defined straight dividing line
10.1.1 The index of refraction to the nearest significant
indicates satisfactory contact between the specimen and prism surfaces.
figure warranted by the accuracy and duplicability of the
7.2 The surface to be used in contact with the prism shall be
measurement. If the index is specified to more than three
flat and shall have a good polish. A second edge surface
significant figures, the wavelength of light for which the
perpendicular to the first and on one end of the specimen shall
measurement was made shall be specified.
be prepared with a fair polish (Note 5). The polished surfaces
NOTE 7—In the case of nonisotropic materials, for example, injection-
shall intersect without a beveled or rounded edge.
andcompression-moldedmaterials,theindexobservedwillbetheaverage
value for a thin layer of small area at a point of contact near the center of
NOTE 5—It has been found possible to prepare a satisfactorily polished
the refractometer prism. For a complete and accurate determination of the
surface by hand polishing small specimens on an abrasive material backed
variationoftheindexthroughoutthetestspecimen,itisnecessarytomake
by a piece of plate glass. Fine emery paper (for example, No. 000
the measurement at more than one point on the surface and within the
Behr-Manning polishing paper) followed by a polishing rouge compound
body of the material. This can be done by preparing a contacting surface
suspended in water on a piece of parchment paper has successfully been
both perpendicular and parallel to the molding pressure or flow.After the
used as the abrasive to produce a polished surface.
test specimen is contacted to the prism it may be translated carefully for
7.3 A minimum of three specimens should be prepared and
short distances along the prism surface in the direction of the light source
while the variation of index is followed with the refractometer. This
measured.
procedure should be repeated a sufficient number of times and for a
sufficientnumberofspecimenstodeterminetherangeofindicesinvolved.
8. Conditioning
Theaveragevalueandtherangeoftheindexreadingsobtainedfromthese
8.1 Conditioning—Condition the test specimens at 23 6 specimens shall be reported if the range exceeds the accuracy of the
measurement. If the variations in index are systematic with the orientation
2°Cand50 65 %relativehumidityfornotlessthan40hprior
of the test specimen, and if these variations exceed those found between
to the test in accordance with Procedure A of Practice D 618.
specimens of the same material, the nature of these variations shall be
In cases of disagreement, the tolerances should be 61°C and
reported with the average value.
62 % relative humidity.
NOTE 8—Care should be taken to work rapidly to avoid changes in the
8.2 Test Conditions—Conduct tests at 23 6 2°C and 50 6 refractiveindexoftheplasticduetoitsabsorptionofthecontactingliquid.
5 % relative humidity, unless otherwise directed in a pertinent
10.1.2 The temperature in degrees Celsius at which the
specification. In cases of
...
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