ASTM D7133-21

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Designation: D7133 − 16 D7133 − 21
Standard Test Method for
Polyurethane Raw Materials: Instrumental Measurement of
Tristimulus CIELAB Color and Yellowness Index of Liquids
This standard is issued under the fixed designation D7133; 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.
1. Scope*
1.1 This test method provides an instrumental method for measuring the CIELAB color and Yellowness Index (YI) of liquid
polyurethane raw materials. The CIELAB and YI results are derived from mathematical manipulation of CIE tristimulus values
in accordance with Practices E308 and E313, respectively.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to
inch-pound units that are provided for information only and are not considered standard.
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.
NOTE 1—There is no known ISO equivalent to this standard.
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:
D883 Terminology Relating to Plastics
D1193 Specification for Reagent Water
E180 Practice for Determining the Precision of ASTM Methods for Analysis and Testing of Industrial and Specialty Chemicals
(Withdrawn 2009)
E284 Terminology of Appearance
E308 Practice for Computing the Colors of Objects by Using the CIE System
E313 Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color Coordinates
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2935 Practice for Evaluating Equivalence of Two Testing Processes
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.22 on Cellular Materials - Plastics
and Elastomers.
Current edition approved Sept. 1, 2016Oct. 1, 2021. Published September 2016October 2021. Originally approved in 2005. Last previous edition approved in 20112016
as D7133 - 11.D7133 - 16. DOI:10.1520/D7133-16.DOI:10.1520/D7133-21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
*A Summary of Changes section appears at the end of this standard
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D7133 − 21
3. Terminology
3.1 Definitions—For definitions of terms that appear in this test method, refer to Terminologies E284, D883, and the terminology
section of Practice E308. For terms relating to precision and bias and associated issues, the terms used in this standard are defined
in accordance with Terminology E456.
4. Summary of Test Method
4.1 The color of the total transmitted light is measured by a spectrophotometer in CIE tristimulus values under CIE standard
illuminant D65 and CIE 1964 supplementary standard observer commonly called the 10° standard observer. These values are then
converted by the appropriate equations to the CIELAB color scale and the Yellowness Index. L*a*b* and YI values are reported.
5. Significance and Use
5.1 CIELAB is a visual-based scale that is used to specify color and set color tolerances for the polyurethane industry.
5.2 Yellowness Index specifies the degree of departure of the sample from colorless towards yellow. This index is only suitable
for clear liquids with degrees of saturation in yellow (dominant transmission wavelength in the 570 to 580 nm range). It is used
to set tolerances for appropriate polyurethane raw materials.
5.3 This test method does not include provisions for materials with fluorescence or visible haze (usually greater than 5 % haze).
5.4 Before proceeding with this test method, make reference to the specification of the material being tested. Any test specimen
preparation, conditioning, dimensions, or testing parameters or combination thereof, covered in the materials specification shall
take precedence over those mentioned in this test method. If there are no material specifications, then the default conditions apply.
6. Interferences
6.1 This test method is to be used to compare samples only when they are measured under the same conditions.
6.1.1 The medium in the cuvette used during standardization of the instrument will have an effect on the measured results. Light
mineral oil is recommended, however, distilled water is a suitable substitute but a note of the substitution must be included in any
report of the results.
6.1.2 The temperature of the sample is also expected to affect the results obtained.
7. Apparatus
7.1 Instrument—A hemispherical geometry (integrating sphere) spectrophotometer capable of total transmission (TTRAN) CIE
tristimulus measurement through a cuvette. TTRANcuvette that includes both the regularly transmitted portion and the diffused
portion of the incident light. The instrument must be capable of converting CIE XYZ tristimulus values to the CIELAB color scale
as defined in Practice E308 using CIE D65 standard illuminant and 10° standard observer. The instrument must also be capable
of converting CIE XYZ tristimulus values to the Yellowness Index value defined in Practice E313 using CIE D65 standard
illuminant and 10° standard observer. The instrument is to meet the manufacturer’s requirements for calibration. For highly
transparent samples, such as the polyols in Tables 1 and 2, Tables 1 and 2, spectrophotometers or tristimulus colorimeters without
a spherical geometry are acceptable for use with equivalent results.acceptable.
7.2 Sample Cuvettes—The cuvette must have a 20 6 0.06 mm pathlength. The entrance and exit windows shall be parallel,
colorless, clear and unaffected by the material being analyzed. The optical properties of the cuvette used during standardization
of the instrument and the cuvette used for measuring samples (if not the same cuvette) must be matched. This is determined by
proving that the variation, if any, in the different cuvettes used do not affect the measured value of a standard sample. Glass or
plastic cuvettes are both acceptable.
8. Reagents
8.1 Mineral Oil—Colorless NF or FCC grade light mineral oil.
D7133 − 21
TABLE 1 CIELAB Round Robin Data
L* values
A B C D
Standard Material Viscosity Average S S r R
r R
Mineral Oil
PMDI A 200 mPa s 44.93 0.05 0.76 0.15 2.13
(200 cP)
PMDI B 750 mPa s 1.64 0.03 0.26 0.10 0.74
(750 cP)
Polyol A 475 mPa s 99.88 0.03 0.14 0.07 0.40
(475 cP)
Polyol B 6500 mPa s 96.01 0.11 0.85 0.31 2.37
(6500 cP)
a* values
A B C D
Standard Material Viscosity Average S S r R
r R
Mineral Oil
PMDI A 200 mPa s 45.80 0.03 0.26 0.07 0.72
(200 cP)
PMDI B 750 mPa s 9.17 0.12 1.01 0.33 2.82
(750 cP)
Polyol A 475 mPa s –0.13 0.00 0.02 0.01 0.07
(475 cP)
Polyol B 6500 mPa s –1.82 0.03 0.26 0.07 0.72
( 6500 cP)
b* values
A B C D
Standard Material Viscosity Average S S r R
r R
Mineral Oil
PMDI A 200 mPa s 72.88 0.09 4.72 0.25 13.22
(200 cP)
PMDI B 750 mPa s (750 cP) 2.37 0.08 0.44 0.23 1.23
Polyol A 475 mPa s 0.63 0.01 0.10 0.03 0.29
(475 cP)
Polyol B 6500 mPa s 12.32 0.06 1.33 0.16 3.74
( 6500 cP)
A
S = within laboratory standard deviation of individual replicates.
r
B
S = between laboratories standard deviation of means of replicates.
R
C
r = within laboratory critical interval between individual replicates (2.8 × S )—repeatability.
r
D
R = between laboratory critical interval between means of replicates (2.8 × S )—reproducibility.
R
TABLE 2 Yellowness Index Round Robin Data
YI values
A B C D
Standard Material Viscosity Average S S r R
r R
Mineral Oil
Polyol A 475 mPA s 1.08 0.01 0.19 0.04 0.52
(475 cP)
Polyol B 6500 mPa s 21.60 0.10 4.60 0.28 12.88
(6500 cP)
A
S = within laboratory standard deviation of individual replicates.
r
B
S = between laboratories standard deviation of means of replicates.
R
C
r = within laboratory critical interval between individual replicates (2.8 × S )—repeatability.
r
D
R = between laboratory critical interval between means of replicates (2.8 × S )—reproducibility.
R
8.2 Distilled Water—Colorless distilled water conforming to Type IV of Specification D1193.
9. Hazards
9.1 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,
even when conducted rapidly, can cause contamination of the sample with insoluble urea. Therefore, blanket the sample with dry
air or nitrogen at all times. (Warning—Diisocyanates are eye, skin and respiratory irritants at concentrations above the
occupational exposure limit (TLV or PEL). Diisocyanates can cause skin and respiratory sensitization (asthma) in some people.
Once sensitized, it is essential to limit further exposure to diisocyanates. Use a combination of engineering controls and personal
protective equipment, including respiratory, skin and eye protection, to prevent over-exposure to diisocyanates. Consult the product
suppliers’ Safety Data Sheet (SDS) for more detailed information about potential health effects and other specific safety and
handling instructions for the product.)
D7133 − 21
10. Sampling Sampling, Test Specimens and Test Specs and Units
10.1 Test samples are to be homogeneous and representative of the liquid being tested.
10.2 Do not touch the entrance and exit windows of the cuvette through which incident and transmitted light will pass except to
clean them.
10.3 The CIELAB values, L*, a*, and b*, have no units associated with them.
10.4 The Yellowness Index value, YI, has no unit associated with it.
9.5 Since organic isocyanates react with atmospheric moisture, take special precautions in sampling. Usual sampling methods,
even
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