ASTM D4878-23

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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
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Designation: D4878 − 15 D4878 − 23
Standard Test Methods for
Polyurethane Raw Materials: Determination of Viscosity of
Polyols
This standard is issued under the fixed designation D4878; 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 These test methods (A and B) determine the viscosity of polyols in the range from 10 to 100 000 mPa·s(cP) at 25°C. Test
Method A is a rotational procedure for determining dynamic viscosity. Test Method B is a general procedure for kinematic viscosity
of transparent polyols. (See Note 1.)
1.2 The values stated in SI units are to be regarded as the standard. Other equivalent units are provided because of current common
usage.
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 healthsafety, health, and environmental practices and determine
the applicability of regulatory limitations prior to use.
NOTE 1—Test Method A is equivalent to ISO 3219. Test Method B is equivalent to ISO 3104.
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:
D445 Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and Calculation of Dynamic Viscosity)
D446 Specifications and Operating Instructions for Glass Capillary Kinematic Viscometers
D883 Terminology Relating to Plastics
E456 Terminology Relating to Quality and Statistics
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2251 Specification for Liquid-in-Glass ASTM Thermometers with Low-Hazard Precision Liquids
E2935 Practice for Evaluating Equivalence of Two Testing Processes
2.2 ISO Standards:
ISO 3104 Petroleum Products—Transparent and Opaque Liquids—Determination of Kinematic Viscosity and Calculation of
Dynamic Viscosity
These test methods are 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 May 1, 2015May 1, 2023. Published June 2015May 2023. Originally approved in 1988. Last previous edition approved in 20082015 as
D4878 - 08.D4878 - 15. DOI: 10.1520/D4878-15.10.1520/D4878-23.
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.
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
D4878 − 23
ISO 3219 Plastics—Polymers/Resins in the Liquid State of as Emulsions or Dispersions—Determination of Viscosity Using a
Rotational Viscometer with Defined Shear Rate
3. Terminology
3.1 For definitions of terms used in these test methods see Terms used in this standard are defined in accordance with Terminology
D883, 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.
4. Significance and Use
4.1 These test methods are suitable for research or as quality control or specification tests.
4.2 Viscosity measures the resistance of a fluid to uniformly continuous flow without turbulence or other forces.
5. Sampling
5.1 Polyester and polyether polyols contain molecules covering an appreciable range of molecular weights. These can fractionate
during solidification. Unless the material is a finely ground solid it is necessary to melt (using no higher temperature than
necessary) and mix the polyol well before removing a sample for analysis. Many polyols are hygroscopic and care should be taken
hygroscopic, therefore exercise care to provide minimum exposure to atmospheric moisture during the sampling.
TEST METHOD A—ROTATIONAL VISCOSITY
6. Summary of Test Method
6.1 The viscosity is measured by determining the torque on a spindle rotating at constant speed in the liquid sample at 25 6 0.1°C.
Generation of comparative data using this method requires agreement on the speed, spindle, temperature, time of rotation, and
torque range of the instrument used.
7. Apparatus
7.1 Constant-Temperature Bath, capable of maintaining a temperature of 25 6 0.1°C is to be used. Water, water and glycerin, or
oil is used as the heating medium and the bath is to be provided with heating, circulating, and thermostatting devices.
7.2 Bath and Sample Thermometers, graduated in 0.1°C subdivisions and standardized for the range of use to the nearest 0.01°C.
ASTM Saybolt Viscosity Thermometers having ranges from 19 to 27°C and 49 to 57°C, as specified, and conforming to the
requirements for Thermometers S117C and S64C, respectively, as prescribed in Specification E2251 are recommended. Any other
thermometric device of equal or better accuracy is also acceptable.
7.3 Rotational Viscometer—Capable of user defined speed and spindle combinations. An instrument that is capable of providing
the shear rate is recommended. The calibration of the instrument is to be checked periodically by measuring the viscosity of NIST
traceable standard fluids.
8. Solvent
8.1 Cleaning Solvent—methanol or acetone, reagent grade. Any solvent in which the polyol is completely miscible is acceptable.
9. Preparation of Sample
9.1 The preparation of a homogeneous sample is of primary importance in viscosity measurements. A non-uniform temperature
distribution as well as the presence of air bubbles and traces of extraneous material are to be avoided. The sample must be
thoroughly mixed and the temperature measured at several locations in the sample vessel before determining the viscosity.
10. Preparation of Apparatus
10.1 Follow the manufacturer’s instructions to set up the instrument and ensure that the viscometer is level.
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11. Choice of Temperature
11.1 Samples that are liquid and have a viscosity of less than 100 000 mPa·s(cP) at 25°C are to be measured at 25°C.
11.2 In cases of interlaboratory studies and higher viscosity samples, all parties are to agree upon a set measurement temperature.
12. Choice of Spindle and Rotational Speed
12.1 Rotational viscometers offer a variety of spindle size and rotational speeds. In the case of non-Newtonian liquids, changing
these factors will cause variation in the results obtained. In general, the following recommendations provide guidance for choosing
the spindle size and speed to be used for a specific sample.
12.1.1 The combination chosen shall generate a torque value between 15 and 90 % of full scale, or that specified by the instrument
manufacturer.
12.1.1.1 If more than one speed/spindle combination will fulfill the requirement of 12.1.1, the combination with the higher speed
will provide higher accuracy and the combination with the lower speed will minimize certain types of non-Newtonian behavior.
12.1.1.2 There must be agreement between the testing laboratory and the submitter on the spindle, speed selection.
13. Procedure
13.1 Using the smallest container recommended by the manufacturer, place sufficient sample to cover the immersion mark on the
viscometer spindle. Cover the container and immerse it to the sample level in a constant temperature bath. Stir occasionally without
trapping air bubbles. Check the temperature at several different locations in the container to ensure uniformity has been achieved.
13.2 After the desired temperature has been observed throughout the sample for 10 min, immerse the viscometer spindle (and the
guard when recommended by the manufacturer) into a sample to the immersion line marked on the spindle. Exercise caution to
avoid air bubbles gathering under the spindle during immersion. If bubbles are observed, detach the spindle, keeping it in the
sample, and stir until the bubbles are released. Reattach the spindle.
13.3 Follow the manufacturer’s instructions to measure the viscosity for the sample using a 15-second rotation time.
13.4 After the analysis, spindles are cleaned with a solvent appropriate for the polyol and equipment used, for example, methanol
or acetone.
14. Calculation
14.1 Multiply the reading by the factor provided by the manufacturer for the speed/spindle combination used to convert the
instrument reading to the viscosity in mPa·s (cP). Most instruments automatically perform this calculation.
15. Report
15.1 Report the following information:
15.1.1 Temperature of test,
15.1.2 Model of viscometer,
15.1.3 Speed of rotation,
15.1.4 Spindle number, and
15.1.5 Viscosity in millipascal seconds (centipoises) [mPa•s(cP)].
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16. Precision and Bias
16.1 Precision—Attempts to develop a precision and bias statement for this test method have not been successful; however, the
precision is expected to be equivalent to that reported by the instrument manufacturer. For this reason, data on precision and bias
cannot be given. Because this test method does not contain a numerical precision and bias statement, it shall not be used as a referee
test method in case of dispute. Anyone wishing to participate in the development of precision and bias data should are to contact
the Chairman,Chair, Subcommittee D20.22 (Section D20.22.01), ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428.
16.2 Bias—The bias of this test method has not yet been determined.
TEST METHOD B—KINEMATIC VISCOSITY
17. Summary of Test Method
17.1 The viscosity of polyols is measured by determining the time it takes a fixed volume of liquid to flow under gravity control
through a calibrated capillary glass viscometer under a reproducible driving head at 25 6 0.1°C. The kinematic viscosity is
determined by multiplying the flow time by the calibration factor of the viscometer.
18. Apparatus
18.1 Additional details of equipment can be found in Specifications D446.
18.2 Constant-Temperature Bath, capable of maintaining a temperature of 25 6 0.1°C and 50 6 0.1°C is to be used. Water, water
and glycerin, oil, or any other transparent thermal transfer liquid is to be used as the heating medium and the bath is to be of
sufficient depth and to be provided with heating, circulating, and thermostatting devices.
18.3 Thermometers, graduated in 0.1°C subdivisions and standardized for the range of use to the nearest 0.01°C. ASTM Saybolt
Viscosity Thermometers having ranges from 19 to 27°C and 49 to 57°C, as specified, and conforming to the requirements for
Thermometers S117C and S64C,
...