ASTM D8162-20a

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Designation: D8162 − 20 D8162 − 20a
Standard Test Method for
Determination of the Apparent Viscosity of Thermoplastic
Pavement Marking Materials using a Rotational Viscometer
with Temperature Control Heating Unit
This standard is issued under the fixed designation D8162; 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 covers the sample preparation and testing procedure needed to determine the apparent viscosity of a
thermoplastic pavement marking formulation at elevated temperatures to the specimen.
1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are customary units
and are provided as a courtesy to the user.
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.
2. Referenced Documents
2.1 ASTM Standards:
D883 Terminology Relating to Plastics
D7307 Practice for Sampling of Thermoplastic Traffic Marking Materials
D7308 Practice for Sample Preparation of Thermoplastic Pavement Marking Materials
E177 Practice for Use of the Terms Precision and Bias in ASTM Test Methods
E284 Terminology of Appearance
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
E2975 Test Method for Calibration or Calibration Verification of Concentric Cylinder Rotational Viscometers
3. Terminology
3.1 The terms and definitions in Terminology D883 and Terminology E284 apply to this test method.
3.2 Definitions of Terms Specific to This Standard:
This test method is under the jurisdiction of ASTM Committee D01 on Paint and Related Coatings, Materials, and Applications and is the direct responsibility of
Subcommittee D01.44 on Traffic Coatings.
Current edition approved June 1, 2020Sept. 1, 2020. Published September 2020. Originally approved in 2020. Last previous edition approved in 2020 as D8162 – 20. DOI:
10.1520/D8162-20.10.1520/D8162-20A.
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.
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D8162 − 20a
3.2.1 apparent viscosity, n—the viscosity determined by this test method can be expressed in millipascal seconds, Centipoise, and
Poise. Common viscosity units of Poise (P) are related to the SI units by the equivalency 1 cP = 1 mPa·s.
3.2.1.1 Discussion—
An apparent viscosity value may vary with the spindle and rotational speed elected for measuring non-Newtonian materials.
3.2.2 thermoplastic pavement marking (material), n—a highly filled 100 % total solids highway marking system that when heated
to a molten state can be extruded or sprayed onto a road surface. Retroreflective optics are applied (dropped on) to the surface of
the molten marking immediately after application to provide, when cooled, a solid durable delineator or thermoplastic pavement
marking usually melted to ~218°C (425°F)
3.2.3 viscosity, n—the ratio of shear stress to shear rate.
3.2.3.1 Discussion—
The viscosity of a liquid is a measure of the resistance to flow of the liquid. The SI unit of dynamic viscosity is the pascal second.
For a Newtonian liquid, the viscosity is constant at all shear rates. For a non-Newtonian liquid, viscosity will vary depending on
shear rate.
4. Summary of Test Method
4.1 This viscosity method is used to determine the apparent viscosity of thermoplastic pavement marking products at elevated
temperatures. Apparent viscosity is determined under temperature equilibrium conditions using a rotating spindle type viscometer.
The torque on a spindle rotating in a temperature-controlled sample holder containing a small amount of sample is used to measure
the relative resistance to rotation. A factor is applied to the torque reading to yield the viscosity in mPa·s (cP or Poise).
5. Significance and Use
5.1 This test method is used to measure the apparent viscosity of thermoplastic pavement marking at elevated temperatures.
Elevated temperature viscosities of thermoplastic pavement marking may be related to the properties of coatings, adhesives, and
composite thermoplastics. This method is helpful in determining the flow properties which can be used in determining
processability when applied to the road surface.
5.2 Thermoplastic pavement markings may be applied to the road surface in several different ways. Typical methods of application
are screed extrude, ribbon extrude, thin film spray, and standard spray. Proper application depends on the viscosity of the
thermoplastic material at application temperatures for the method being used. Thin-line applied thermoplastic pavement marking,
for example, requires a relatively lower viscosity. Screed extrude applied thermoplastic requires a higher viscosity.
5.3 Materials of the type described in this procedure may be non-Newtonian, and as such, the apparent viscosity will be a function
of shear rate under the conditions of test. Although the viscometer described in this test method operates under conditions of
relatively low shear rate, differences in shear effect can exist depending upon the spindle and rotational speed conditions selected
for the test program. Comparisons between non-Newtonian viscosity values should be made only for measurements made with
similar viscometers under conditions of equivalent shear. For this method, “torpedo” spindles are recommended. Spindles
considered torpedo spindles are ~1-in. long and come in many diameters with a 45° conical bottom. A diameter that is half the
diameter of the thimbles used is recommended. If large glass beads are used in the pavement marking formulation, a smaller
diameter spindle may be needed so the beads do not cause an impedance of the spindle due to a jamming between the inside wall
of the thimble and the spindle.
6. Interferences
6.1 Thermoplastic pavement marking products can change in viscosity over extended periods of heat history; therefore, it is
recommended that these type viscosities be performed on product samples which have the same heat history in order to lower
deviation of comparative results.
6.2 Thermoplastic pavement marking products contain glass beads which can settle quickly if the formulation is not stirred
constantly. Because of that fact, some formulations may have too low of viscosity to stay homogeneous at the commonly used
processing temperature 218°C (425°F) for any length of time for the test sample’s temperature and viscosity to be stable. Therefore,
a pre-set time-period may be necessary after the sample is placed in the thimble and heater at which to record the viscosity.
D8162 − 20a
7. Apparatus
7.1 Viscometer, Rotational—The essential instrumental required providing the minimum rotational viscometer analytical
capabilities include:
7.1.1 A drive motor, to apply a unidirectional torque to the specimen constant to 61 %;
7.1.2 A force sensor to measure the torque developed by the specimen readable to within 61 %;
7.1.3 A coupling shaft or other means to transmit the rotational force from the motor;
7.1.4 A spindle, rotational element, geometry or tool to fix the specimen between the drive shaft and a stationary position. The
spindle has a torpedo shape as in Fig. 1. Note: For this testing we are recommending a nominal length (L) of 33.0 mm and a
diameter (D) of 11.8 mm. Different sizes can be chosen to be run with agreement between the buyer and seller of the product.
Where more than one spindle is available for the range selected, choose a spindle that produc
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