ASTM D542-22

Standard Test Method for Index of Refraction of Transparent Organic Plastics

SIGNIFICANCE AND USE
4.1 This test method measures a fundamental property of matter which is useful for the control of purity and composition for simple identification purposes, and for optical parts design. This test method is capable of readability to four figures to the right of the decimal point.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Aug-2022
• ICS: 83.080.01 - Plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.40 - Optical Properties

Relations

• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM C162-23 - Standard Terminology of Glass and Glass Products
• Effective Date: 01-Oct-2023
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM D883-17 - Standard Terminology Relating to Plastics
• Effective Date: 15-Aug-2017
• Refers: ASTM C162-05(2015) - Standard Terminology of<brk type="line"/> Glass and Glass Products
• Effective Date: 01-Nov-2015
• Refers: ASTM E456-13ae1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 15-Nov-2013

Overview

ASTM D542-22: Standard Test Method for Index of Refraction of Transparent Organic Plastics sets forth a widely recognized procedure for measuring the refractive index of transparent organic plastic materials. Developed by ASTM International, this test method employs a refractometer-based approach to determine an essential optical property crucial for material identification, purity control, and design of optical components. Achieving readings accurate to four decimal places, ASTM D542-22 provides repeatable and reliable results for manufacturers, researchers, and quality assurance professionals working with transparent polymers.

Key Topics

• Index of Refraction Measurement: The standard outlines a refractometer method suitable for the diverse refractive indices found in transparent plastics, ensuring high-precision results on optically homogeneous specimens.
• Specimen Requirements: To ensure reliable refractive index measurements, test specimens must be optically uniform and free from surface imperfections, with polished, flat surfaces optimizing contact with the refractometer prism.
• Test Apparatus: Use of an Abbe or similar refractometer with an appropriate white light source and a compatible contacting liquid is specified to avoid surface damage to specimens during testing.
• Sampling and Conditioning: The method requires statistically adequate sampling and specimen conditioning at 23 ± 2°C and 50 ± 10% relative humidity for no less than 40 hours prior to testing, supporting consistency in results across different labs and materials.
• Precision and Bias: ASTM D542-22 provides principles for evaluating laboratory precision and bias, referencing interlaboratory studies and associated practices to help users establish their own data validity.

Applications

The practical uses of ASTM D542-22 are widespread in fields that demand precise optical properties in plastic materials:

• Quality Control in Manufacturing: Producers of transparent plastics use this standard to verify material purity and uniformity, ensuring batches meet required optical specifications.
• Material Identification: The refractive index is a key identifier for various polymers, supporting rapid sorting and verification processes in recycling, forensic analysis, and supply chain management.
• Optical Component Design: Engineers and designers rely on refractive index measurements for the accurate creation of lenses, light guides, sensors, and displays, where optical clarity and performance are essential.
• Research and Development: Laboratories use ASTM D542-22 to benchmark new formulations, improve compositions, and develop innovative materials for specialized optical uses.

Related Standards

Professionals working with ASTM D542-22 may also reference the following related standards to ensure comprehensive compliance and coverage:

• ISO 489: Determination of the Refractive Index of Transparent Plastics - Technically equivalent to ASTM D542-22, this international standard can be used interchangeably in global applications.
• ASTM D618: Practice for Conditioning Plastics for Testing - Specifies environmental conditioning critical to preparation for refractive index testing.
• ASTM D883: Terminology Relating to Plastics - Provides essential definitions for terms used in plastics standards.
• ASTM E284: Terminology of Appearance - Supports consistent understanding of appearance properties in optical testing.
• ASTM E691: Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method - Referenced for best practices in precision and bias determinations.
• ASTM C162: Terminology of Glass and Glass Products - Useful for comparison and classification in mixed-material optical applications.

Conclusion

ASTM D542-22 delivers a robust framework for evaluating the refractive index of transparent organic plastics, empowering manufacturers, laboratories, and designers with a reliable standard for quality assurance and product development. Its alignment with international practices and emphasis on precision make it an essential reference for industries dependent on optical performance and material verification. For optimal results and full compliance, users should consult related standards and rigorously apply the sampling and conditioning guidelines prescribed in ASTM D542-22.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D542 − 22
Standard Test Method for
Index of Refraction of Transparent Organic Plastics
This standard is issued under the fixed designation D542; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* 2.2 ISO Standard:
ISO 489 Determination of the Refractive Index of Transpar-
1.1 This test method covers a procedure for measuring the
ent Plastics—Part A
index of refraction of transparent organic plastic materials.
1.2 A refractometer method is presented. This procedure 3. Terminology
will satisfactorily cover the range of refractive indices found
3.1 Definitions:
for such materials. Refractive index measurements require
3.1.1 Terms used in this standard are defined in accordance
optically homogeneous specimens of uniform refractive index.
with Terminology standards D883 and E284, unless otherwise
specified. For terms relating to precision and bias and associ-
NOTE 1—This test method and ISO 489 are technically equivalent.
ated issues, the terms used in this standard are defined in
1.3 This standard does not purport to address all of the
accordance with Terminology E456.
safety concerns, if any, associated with its use. It is the
3.1.2 dispersion—variation of refractive index with wave
responsibility of the user of this standard to establish appro-
length of light. C162, C14
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use. 3.1.3 index of refraction, n—thenumericalexpressionofthe
1.4 This international standard was developed in accor- ratio of the velocity of light in a vacuum to the velocity of light
dance with internationally recognized principles on standard- in a substance at a specified wavelength. E284, E12
ization established in the Decision on Principles for the
4. Significance and Use
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4.1 This test method measures a fundamental property of
Barriers to Trade (TBT) Committee.
matterwhichisusefulforthecontrolofpurityandcomposition
for simple identification purposes, and for optical parts design.
2. Referenced Documents
This test method is capable of readability to four figures to the
right of the decimal point.
2.1 ASTM Standards:
C162 Terminology of Glass and Glass Products
5. Apparatus
D618 Practice for Conditioning Plastics for Testing
5.1 The apparatus for this test method shall consist of an
D883 Terminology Relating to Plastics
Abbe’ refractometer (Note 2), a suitable source of white light,
E284 Terminology of Appearance
and a small quantity of a suitable contacting liquid (Note 2 and
E456 Terminology Relating to Quality and Statistics
Note 3).
E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
NOTE 2—Other suitable refractometers can be used with appropriate
modification to this procedure as described in Section 7.
NOTE3—Asatisfactorycontactingliquidisonewhichwillnotsoftenor
otherwiseattackthesurfaceoftheplasticwithinaperiodof2hofcontact.
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
The index of refraction of the liquid must be higher, but not less than one
and is the direct responsibility of Subcommittee D20.40 on Optical Properties.
unit in the second decimal place, than the index of the plastic being
Current edition approved Sept. 1, 2022. Published September 2022. Originally
measured; for example, n of the sample = 1.500, n of the contacting
approved in 1939. Last previous edition approved in 2014 as D542 - 14. DOI:
d d
10.1520/D0542-22. liquid ≥1.510.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*A Summary of Changes section appears at the end of this standard
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959. United States
D542 − 22
6. Sampling the index arm of the refractometer until the field seen through
the eyepiece is one-half dark. Adjust the compensator (Amici
6.1 Sampling shall be statistically adequate to ensure that
prisms) drum to remove all color from the field of the ocular.
the specimens were produced and obtained by a process in
Adjust the index arm using the vernier until the dividing line
statistical control.
between the light and dark portions of the field exactly
6.2 Samples can be drawn from any materials presentation
coincides with the intersection of the cross hairs as seen in the
(for example, pellets, film, sheet, fabricated articles, etc.)
eyepiece. Read the value of the index of refraction for the
which permits preparation of a satisfactory specimen as de-
Sodium D Line (see Note 6). Determine the dispersion by
scribed herein.
reading the compensator drum and applying this figure, along
with the index of refraction, to a chart or table supplied with
7. Test Specimens
the instrument.
7.1 The test specimen shall be of a size that will conve-
NOTE 6—Sodium light from a sodium burner or discharge lamp is of
niently fit on the face of the fixed half of the refractometer
use in increasing the precision of this test method as well as making the
prisms(Note4).Aspecimenmeasuring6.3by12.7mmonone
reading of the refractometer easier.
face is usually satisfactory.
9.2 In the case of nonisotropic materials, for example,
NOTE 4—For maximum accuracy in the refractometer method, the
injection- and compression-molded materials, the index ob-
surface contacting the prism must be flat. This surface is judged for
served is the average value for a thin layer of small area at a
flatness, provided the specimen has been satisfactorily polished, by
point of contact near the center of the refractometer prism. For
observing the sharpness of the dividing line between the light and dark
a complete and accurate determination of the variation of the
field as viewed in the ocular. A sharply defined straight dividing line
indicates satisfactory contact between the specimen and prism surfaces. index throughout the test specimen, it is necessary to make the
measurement at more than one point on the surface and within
7.2 The surface to be used in contact with the prism shall be
the body of the material. This can be done by preparing a
flat and shall have a good polish. A second edge surface
contacting surface both perpendicular and parallel to the
perpendicular to the first and on one end of the specimen shall
molding pressure or flow. After the test specimen is contacted
be prepared with a fair polish (Note 5). The polished surfaces
to the prism it may be translated carefully for short distances
shall intersect without a beveled or rounded edge.
along the prism surface in the direction of the light source
NOTE 5—It has been found possible to prepare a satisfactorily polished
while the variation of
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D542 − 14 D542 − 22
Standard Test Method for
Index of Refraction of Transparent Organic Plastics
This standard is issued under the fixed designation D542; 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 (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
C162 Terminology of Glass and Glass Products
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
E284 Terminology of Appearance
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 ISO Standard:
ISO 489 Determination of the Refractive Index of Transparent Plastics—Part A
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms Terms used in this test method, see Terminologies standard are defined in accordance with
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.40 on Optical Properties.
Current edition approved March 1, 2014Sept. 1, 2022. Published March 2014September 2022. Originally approved in 1939. Last previous edition approved in 20132014
as D542 - 13.D542 - 14. DOI: 10.1520/D0542-14.10.1520/D0542-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*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 − 22
Terminology standards D883 and E284, unless otherwise specified. For terms relating to precision and bias and associated issues,
the terms used in this standard are defined in accordance with Terminology E456.
3.1.2 dispersion—variation of refractive index with wave length of light. C162, C14
3.1.3 index of refraction, n—the numerical expression of the ratio of the velocity of light in a vacuum to the velocity of light in
a substance at a specified wavelength. E284, E12
4. Significance and Use
4.1 This test method measures a fundamental property of matter which is useful for the control of purity and composition for
simple identification purposes, and for optical parts design. This test method is capable of readability to four figures to the right
of the decimal point.
5. Apparatus
5.1 The apparatus for this test method shall consist of an Abbe’ refractometer (Note 2), a suitable source of white light, and a small
quantity of a suitable contacting liquid (Note 2 and Note 3).
NOTE 2—Other suitable refractometers can be used with appropriate modification to this procedure as described in Section 7.
NOTE 3—A satisfactory contacting liquid is one which will not soften or otherwise attack the surface of the plastic within a period of 2 h of contact. The
index of refraction of the liquid must be higher, but not less than one unit in the second decimal place, than the index of the plastic being measured; for
example, n of the sample = 1.500, n of the contacting liquid ≥1.510.
d d
6. Sampling
6.1 Sampling shall be statistically adequate to ensure that the specimens were produced and obtained by a process in statistical
control.
6.2 Samples can be drawn from any materials presentation (for example, pellets, film, sheet, fabricated articles, etc.) which permits
preparation of a satisfactory specimen as described herein.
7. Test Specimens
7.1 The test specimen shall be of a size that will conveniently fit on the face of the fixed half of the refractometer prisms (Note
4). A specimen measuring 6.3 by 12.7 mm on one face is usually satisfactory.
NOTE 4—For maximum accuracy in the refractometer method, the surface contacting the prism must be flat. This surface is judged for flatness, provided
the specimen has been satisfactorily polished, by observing the sharpness of the dividing line between the light and dark field as viewed in the ocular.
A sharply defined straight dividing line indicates satisfactory contact between the specimen and prism surfaces.
7.2 The surface to be used in contact with the prism shall be flat and shall have a good polish. A second edge surface perpendicular
to the first and on one end of the specimen shall be prepared with a fair polish (Note 5). The polished surfaces shall intersect
without a beveled or rounded edge.
NOTE 5—It has been found possible to prepare a satisfactorily polished surface by hand polishing small specimens on an abrasive material backed by a
piece of plate glass. Fine emery paper (for example, No. 000 Behr-Manning polishing paper) followed by a polishing rouge compound suspended in water
on a piece of parchment paper has successfully been used as the abrasive to produce a polished surface.
7.3 A minimum of three specimens are prepared and measured.
8. Conditioning
8.1 Conditioning—Condition the test specimens at 23 6 2°C and 50 6 10 % relative humidity for not less than 40 h prior to the
test in accordance with Procedure A of Practice D618. In cases of disagreement, the tolerances should be 61°C and 65 % relative
humidity.
D542 − 22
8.2 Test Conditions—Conduct tests at 23 6 2°C and 50 6 10 % relative humidity, unless otherwise directed in a pertinent
specification. In cases of disagreement, the tolerances shall be 61°C and 65 % relative humidity. If the index of refraction of the
material is found to be highly temperature dependent, then the temperature shall be accurately controlled to 23 6 0.2°C.
9. Procedure
9.1 Remove the hinged illuminating prism from the refractometer, if necessary. Place a source of diffuse polychromatic light so
that even illumination is obtained along the plane of the surface of contact between the specimen and the refractometer prism. Place
a small drop of the suitable contacting liquid on the polished surface of the specimen and then place the specimen in firm contact
with the surface of the prism with the polished side of the specimen toward the specified light source. Determine the index of
refraction in the same manner as specified for liquids. This shall be done by moving the index arm of the refractometer until the
field seen through the eyepiece is one-half dark. Adjust the compensator (Amici prisms) drum to remove all color from the field
of the ocular. Adjust the index arm using the vernier until the dividing line between the light and dark portions of the field exactly
coincides with the intersection of the cross hairs as seen in the eyepiece. Read the value of the index of refraction for the Sodium
D Line (see Note 6). Determine the dispersion by reading the compensator drum and applying this figure, along with the index
of refraction, to a chart or table supplied with the instrument.
NOTE 6—Sodium light from a sodium burner or discharge lamp is of use in increasing the precision of this test method as well as making the reading
of the refractometer easier.
9.2 In the case of nonisotropic materials, for example, injection- and compression-molded materials, the index observed is the
average value for a thin layer of small area at a point of contact near the center of the refractometer prism. For a complete and
accurate determination of the variation of the index throughout the test specimen, it is necessary to make the measurement at more
than one point on the surface and within the body of the material. This can be done by preparing a contacting surface b
...