ASTM D7836-13(2020)

Standard Test Methods for Measurement of Yield Stress of Paints, Inks and Related Liquid Materials

SIGNIFICANCE AND USE
5.1 The yield stress of a material is a measure of the amount of force required to initiate movement of that material in a pipe, through a pump, or from nozzle. The yield stress also characterizes the ability of the material to maintain particles in suspension. Along with viscosity measurements, yield stress measurements have been useful in establishing root causes of flow problems such as excessive orange peel and sagging and in explaining resistance to such problems. After a coating has been applied, flow and leveling tends to be inversely related to yield stress and sag resistance tends to be directly related to yield stress. The ability of an automotive basecoat to keep aluminum and/or mica flakes oriented has been related to yield stress (direct relationship).
SCOPE
1.1 These test methods cover three approaches for determining yield stress values of paints, inks and related liquid materials using rotational viscometers. The first method uses a rotational viscometer with coaxial cylinder, cone/plate, or plate/plate geometry. The second method uses a rheometer operating in controlled stress mode with similar geometries. The third method uses a viscometer with a vane spindle.  
1.2 A non-rotational technique, the falling needle viscometer (FNV), also can be used to measure yield stress values in paints, inks and related materials. See Test Methods D5478, Test Method D, Yield Stress Determination for details.  
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: 30-Nov-2020
• ICS: 87.040 - Paints and varnishes
• ICS: 87.080 - Inks. Printing inks
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.24 - Physical Properties of Liquid Paints & Paint Materials

Relations

• Refers: ASTM D5478-13 - Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
• Effective Date: 01-Feb-2013
• Refers: ASTM D3925-02(2010) - Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings
• Effective Date: 01-Dec-2010
• Refers: ASTM D5478-09 - Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
• Effective Date: 01-Feb-2009
• Refers: ASTM D5478-98(2003) - Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
• Effective Date: 01-Dec-2003
• Refers: ASTM D3925-02 - Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings
• Effective Date: 10-Aug-2002
• Refers: ASTM D5478-98 - Standard Test Methods for Viscosity of Materials by a Falling Needle Viscometer
• Effective Date: 10-Jun-1998
• Refers: ASTM D3925-91(1996) - Standard Practice for Sampling Liquid Paints and Related Pigmented Coatings
• Effective Date: 15-Sep-1991

Overview

ASTM D7836-13(2020) - Standard Test Methods for Measurement of Yield Stress of Paints, Inks and Related Liquid Materials defines precise methodologies for determining the yield stress of coatings, paints, inks, and similar liquid materials. The yield stress measurement is critical for characterizing a material’s ability to initiate flow and maintain particle suspension. This standard supports manufacturers and formulators in understanding and optimizing flow behavior, aiding in the prevention of defects such as orange peel and sagging during application. ASTM D7836 was developed with internationally recognized standardization principles, aligning with guidelines from the World Trade Organization Technical Barriers to Trade (TBT) Committee.

Key Topics

• Yield Stress Definition: Yield stress is identified as the critical stress at which a material transitions from behaving as a deformable solid to exhibiting fluid-like flow. It is essential in evaluating how materials respond under force, particularly in processes involving pumping, spraying, or dispensing.
• Test Methods:
  • Rotational Viscometer Techniques: Utilize instruments with coaxial cylinder, cone/plate, or plate/plate geometries. The test involves shearing the material at various speeds and mathematically determining the yield stress by extrapolating data to zero shear rate.
  • Controlled Stress Rheometer: Applies a gradually increasing stress using cone/plate or plate/plate geometry while monitoring the yield stress at which the material begins to move.
  • Vane Spindle Method: Measures yield stress using a spindle with vanes, which is gently immersed in the specimen. The maximum torque reached during slow rotation indicates the yield stress.
  • Falling Needle Viscometer (FNV): A non-rotational alternative referenced within the standard, suitable for materials where structure preservation during testing is critical.
• Sample Handling and Preparation: Ensuring minimal disturbance is vital as handling can affect the sample’s physical structure and the accuracy of the yield stress measurement. Temperature equilibration is also important for reliable results.

Applications

• Paints and Coatings: Determines the suitability of liquid coatings for specific application methods (e.g., spraying, roll-coating), where yield stress influences flow, leveling, and sag resistance.
• Particle Suspension: Relevant in formulations intended to keep pigments, flakes, or fillers in suspension, directly impacting consistency and appearance.
• Process Optimization: Yield stress data informs adjustments in manufacturing and application to minimize defects like sagging and orange peel, and contributes to selecting proper formulation parameters.
• Quality Control: Routine measurement ensures product consistency across batches and supports compliance with industry and client specifications.

Related Standards

• ASTM D3925 – Practice for Sampling Liquid Paints and Related Pigmented Coatings: Provides guidelines for obtaining representative samples, essential for valid yield stress testing.
• ASTM D5478 – Test Methods for Viscosity by a Falling Needle Viscometer: Offers complementary viscosity and yield stress methodologies, especially valuable for shear-sensitive or highly structured materials.

Keywords: yield stress, paints, inks, rotational viscometer, rheometer, particle suspension, flow behavior, sag resistance, ASTM D7836, vane spindle, falling needle viscometer.

By adhering to ASTM D7836-13(2020), industries benefit from standardized, reliable methods for assessing the yield stress of liquid materials, leading to enhanced product performance, reduced waste, and improved customer satisfaction.

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: D7836 − 13 (Reapproved 2020)
Standard Test Methods for
Measurement of Yield Stress of Paints, Inks and Related
Liquid Materials
This standard is issued under the fixed designation D7836; 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 3. Terminology
3.1 vane spindle, n—spindle in which several (4 to 6)
1.1 Thesetestmethodscoverthreeapproachesfordetermin-
rectangular vanes are attached to the shaft giving the appear-
ing yield stress values of paints, inks and related liquid
ance of a cross or star when viewed from the end.
materials using rotational viscometers. The first method uses a
3.1.1 Discussion—A vane spindle can be immersed in a
rotational viscometer with coaxial cylinder, cone/plate, or
specimen without destroying the shear-sensitive structure.
plate/plate geometry. The second method uses a rheometer
operating in controlled stress mode with similar geometries.
3.2 yield stress, n—the critical stress at which a material
The third method uses a viscometer with a vane spindle.
goes from being a deformable solid to showing fluid-like
behavior.
1.2 A non-rotational technique, the falling needle viscom-
3.2.1 Discussion—Examples of such fluids include many
eter (FNV), also can be used to measure yield stress values in
paints and pigment pastes and certain food materials such as
paints, inks and related materials. See Test Methods D5478,
ketchup.
Test Method D, Yield Stress Determination for details.
4. Summary of Test Methods
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
4.1 Test Method A uses a viscometer with coaxial cylinder,
responsibility of the user of this standard to establish appro-
cone/plate, or plate/plate geometry running a several different
priate safety, health, and environmental practices and deter-
low rotational speeds. The materials is sheared at each speed
mine the applicability of regulatory limitations prior to use.
and a shear stress value is measured. By plotting shear stress
1.4 This international standard was developed in accor-
versus shear rate, a dynamic yield stress value is determined by
dance with internationally recognized principles on standard-
extrapolating the data curve to zero shear rate. “Dynamic”
ization established in the Decision on Principles for the
indicatesthatthematerialhasbeenallowedtoflowandthatthe
Development of International Standards, Guides and Recom-
yield stress value is mathematically calculated by using a
mendations issued by the World Trade Organization Technical
best-fit line through the measured data points.
Barriers to Trade (TBT) Committee.
4.2 Test Method B uses a controlled stress rheometer to
determine a yield stress value. This can be done more readily
2. Referenced Documents
with cone/plate or plate/plate geometry, but can also be
2.1 ASTM Standards: accomplished with coaxial cylinder geometry. The rheometer
D3925 Practice for Sampling Liquid Paints and Related applies a stress ramp to the material, starting at zero and
Pigmented Coatings increasing to a preset stress value above the yield stress of the
D5478 Test Methods for Viscosity of Materials by a Falling material. As the torque applied to the spindle increases, the
Needle Viscometer
spindle will start to move when the yield stress in the material
is exceeded. The stress reading at the onset of spindle rotation
is the yield stress value for the material.
These test methods are under the jurisdiction of ASTM Committee D01 on 4.3 TestMethodC uses a rotational viscometer or rheometer
Paint and Related Coatings, Materials, and Applications and are the direct
with a vane spindle immersed in the material.The vane spindle
responsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints &
is rotated slowly at a fixed speed and the torque value is
Paint Materials.
recorded continuously. The yield stress value is determined
Current edition approved Dec. 1, 2020. Published December 2020. Originally
approved in 2013. Last previous edition approved in 2013 as D7836 – 13. DOI:
when the torque value reaches a maximum.
10.1520/D7836-13R20.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 5. Significance and Use
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
5.1 The yield stress of a material is a measure of the amount
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. of force required to initiate movement of that material in a
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7836 − 13 (2020)
pipe, through a pump, or from nozzle. The yield stress also necessary. Cone/plate or plate/plate geometry is typically used
characterizes the ability of the material to maintain particles in because the specimen undergoes minimal disturbance when it
suspension. Along with viscosity measurements, yield stress is placed on the plate. When using coaxial cylinder geometry,
measurements have been useful in establishing root causes of the spindle is immersed causing disturbance to the material
flow problems such as excessive orange peel and sagging and structure; therefore, time must be allowed for the specimen to
in explaining resistance to such problems. After a coating has reestablish its structure before proceeding with the test. The
been applied, flow and leveling tends to be inversely related to smaller sample size required for cone/plate or plate/plate
yield stress and sag resistance tends to be directly related to geometry permits rapid determination of the yield stress value
yield stress. The ability of an automotive basecoat to keep because temperature equilibration of the specimen is quickly
aluminum and/or mica flakes oriented has been related to yield established. The stress
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