ASTM D7836-13

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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-May-2013
• 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

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D7836 − 13
Standard Test Methods for
Measurement of Yield Stress of Paints, Inks and Related
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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 3.2 yield stress, n—the critical stress at which a material
goes from being a deformable solid to showing fluid-like
1.1 Thesetestmethodscoverthreeapproachesfordetermin-
behavior.
ing yield stress values of paints, inks and related liquid
3.2.1 Discussion—Examples of such fluids include many
materials using rotational viscometers. The first method uses a
paints and pigment pastes and certain food materials such as
rotational viscometer with coaxial cylinder, cone/plate, or
ketchup.
plate/plate geometry. The second method uses a rheometer
operating in controlled stress mode with similar geometries.
4. Summary of Test Methods
The third method uses a viscometer with a vane spindle.
4.1 Test Method A uses a viscometer with coaxial cylinder,
1.2 A non-rotational technique, the falling needle viscom-
cone/plate, or plate/plate geometry running a several different
eter (FNV), also can be used to measure yield stress values in
low rotational speeds. The materials is sheared at each speed
paints, inks and related materials. See Test Methods D5478,
and a shear stress value is measured. By plotting shear stress
Test Method D, Yield Stress Determination for details.
versus shear rate, a dynamic yield stress value is determined by
1.3 This standard does not purport to address all of the
extrapolating the data curve to zero shear rate. “Dynamic”
safety concerns, if any, associated with its use. It is the
indicates that the material has been allowed to flow and that the
responsibility of the user of this standard to establish appro-
yield stress value is mathematically calculated by using a
priate safety and health practices and determine the applica-
best-fit line through the measured data points.
bility of regulatory limitations prior to use.
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
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
3. Terminology
is the yield stress value for the material.
3.1 vane spindle, n—spindle in which several (4 to 6)
4.3 TestMethodC uses a rotational viscometer or rheometer
rectangular vanes are attached to the shaft giving the appear-
with a vane spindle immersed in the material.The vane spindle
ance of a cross or star when viewed from the end.
is rotated slowly at a fixed speed and the torque value is
3.1.1 Discussion—A vane spindle can be immersed in a
recorded continuously. The yield stress value is determined
specimen without destroying the shear-sensitive structure.
when the torque value reaches a maximum.
5. Significance and Use
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These test methods are under the jurisdiction of ASTM Committee D01 on
5.1 The yield stress of a material is a measure of the amount
Paint and Related Coatings, Materials, and Applications and are the direct
of force required to initiate movement of that material in a
responsibility of Subcommittee D01.24 on Physical Properties of Liquid Paints and
pipe, through a pump, or from nozzle. The yield stress also
Paint Materials.
characterizes the ability of the material to maintain particles in
Current edition approved June 1, 2013. Published July 2013. DOI: 10.1520/
D7836-13.
suspension. Along with viscosity measurements, yield stress
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
measurements have been useful in establishing root causes of
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
flow problems such as excessive orange peel and sagging and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. in explaining resistance to such problems. After a coating has
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