ASTM D7490-13

Standard Test Method for Measurement of the Surface Tension of Solid Coatings, Substrates and Pigments using Contact Angle Measurements

SIGNIFICANCE AND USE
5.1 The method described in this standard is based on the concept that the total free energy at a surface is the sum of contributions from different intermolecular forces, such as dispersion, polar and hydrogen bonding. There are other techniques that employ three components (dispersion, polar and hydrogen bonding). These methods are further complicated by needing three to five test liquids and are not practical for routine testing. This method uses contact angles of two liquids to provide data for the calculation of two components, dispersion, γsd, and polar, γsp.  
5.2 Dispersion and polar component data, along with the total solid surface tension, are useful for explaining or predicting wetting or adhesion, or both, of coatings on pretreatments, substrates and other coatings. Low solid surface tension values often are a sign of contamination and portend potential wetting problems. High polar components may signal polar contamination. There is evidence in the literature that matching of polar components of topcoats and primers gives better adhesion.4  
5.3 Solid surface tensions of pigments, particularly the polar components, may be useful in understanding dispersion problems or to provide signals for the composition of dispersants and mill bases. However, comparison of pigments may be difficult if there are differences in the roughness or porosity, or both, of the disks prepared from them.  
5.4 Although this technique is very useful in characterizing surfaces, evaluating surface active additives and explaining problems, it is not designed to be a quality control or specification test.
SCOPE
1.1 This test method describes a procedure for the measurement of contact angles of two liquids, one polar and the other nonpolar, of known surface tension on a substrate, pigment (in the form of a disk), or cured or air dried coating in order to calculate the surface properties (surface tension and its dispersion and polar components) of the solid.  
1.2 The total solid surface tension range that can be determined using this method is approximately 20 to 60 dyn/cm.  
1.3 The values stated in CGS units (dyn/cm) are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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: 30-Jun-2013
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.23 - Physical Properties of Applied Paint Films

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7490 − 13
Standard Test Method for
Measurement of the Surface Tension of Solid Coatings,
Substrates and Pigments using Contact Angle
1
Measurements
This standard is issued under the fixed designation D7490; 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 Definitions:
1.1 This test method describes a procedure for the measure-
ment of contact angles of two liquids, one polar and the other
3.1.1 contact angle, n—the interior angle that a drop makes
nonpolar, of known surface tension on a substrate, pigment (in
between the substrate and a tangent drawn at the intersection
the form of a disk), or cured or air dried coating in order to
between the drop and the substrate as shown in Fig. 1; this is
calculate the surface properties (surface tension and its disper-
the angle formed by a liquid at the three phase boundary where
sion and polar components) of the solid.
a liquid, gas (air) and solid intersect.
1.2 The total solid surface tension range that can be deter-
3.1.2 dispersion component, n—the component of solid
mined using this method is approximately 20 to 60 dyn/cm.
surface tension that is related to intermolecular attraction
caused by nonpolar dispersion forces.
1.3 The values stated in CGS units (dyn/cm) are to be
regarded as standard. No other units of measurement are
3.1.3 polar component, n—the component of solid surface
included in this standard.
tension that is related to polar forces, such as hydrogen
bonding and ion-dipole forces.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
3.1.4 solid surface tension, n—the surface tension of a solid
responsibility of the user of this standard to establish appro-
surface; this parameter cannot be measured directly, but must
priate safety and health practices and determine the applica-
be determined by extrapolation of polymer melt or solution
bility of regulatory limitations prior to use.
datato100 %solidsorbycontactangleswithliquidsofknown
surface tension.
2. Referenced Documents
3.1.5 surface energy, n—excess free energy of surface
2
2.1 ASTM Standards:
molecules compared to those of the bulk material; arises from
D1193 Specification for Reagent Water
unbalanced molecular cohesive forces at a surface that cause
D5725 Test Method for Surface Wettability andAbsorbency
the surface to contract and behave like a film or membrane
of Sheeted Materials Using an Automated Contact Angle
2
(units are energy/unit areas such as joules/cm ).
3
Tester (Withdrawn 2010)
D7334 Practice for Surface Wettability of Coatings, Sub- 3.1.6 surface tension, n—the force necessary to break the
strates and Pigments by Advancing Contact Angle Mea-
surface of a film of a given length (units are force/length, such
surement
as dyn/cm or newtons/m); the same numerically as surface
energy, but different units.
1 4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D01 on Paint
and Related Coatings, Materials, andApplications and is the direct responsibility of
4.1 Contact angles of drops of distilled water and di-
Subcommittee D01.23 on Physical Properties of Applied Paint Films.
Current edition approved July 1, 2013. Published August 2013. Originally
iodomethane (methylene iodide) are measured on the surface
approved in 2008. Last previous edition approved in 2008 as D7394 – 08. DOI:
of interest. The two values are then substituted into two
10.1520/D7490-13.
2 separate expressions of the Owens-Wendt-Kaelble equation
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
(one for each liquid). This results in two equations in two
Standards volume information, refer to the standard’s Document Summary page on
unknowns, which are then solved for the dispersion and polar
the ASTM website.
3 components of surface tension. The sum of the components is
The last approved version of this historical standard is referenced on
www.astm.org. the surface tension of the solid.
*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
1

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D7490 − 13
6.1.4 Low humidity (<40 % RH) when water is the test
liquid such that the contact angle changes rapidly.
7. Apparatus
7.1 Goniometer—An instrument consisting of a controlled
light source, a stage to hold the test specimen, and a micro-
scope or c
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
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
of the standard as published by ASTM is to be considered the official document.
Designation: D7490 − 08 D7490 − 13
Standard Test Method for
Measurement of the Surface Tension of Solid Coatings,
Substrates and Pigments using Contact Angle
1
Measurements
This standard is issued under the fixed designation D7490; 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 Scope*
1.1 This test method describes a procedure for the measurement of contact angles of two liquids, one polar and the other
nonpolar, of known surface tension on a substrate, pigment (in the form of a disk), or cured or air dried coating in order to calculate
the surface properties (surface tension and its dispersion and polar components) of the solid.
1.2 The total solid surface tension range that can be determined using this method is approximately 20 to 60 dynes/cm.dyn/cm.
1.3 The values stated in SICGS units (dyn/cm) are to be regarded as standard. No other units of measurement are included in
this standard.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D1193 Specification for Reagent Water
D5725 Test Method for Surface Wettability and Absorbency of Sheeted Materials Using an Automated Contact Angle Tester
3
(Withdrawn 2010)
D7334 Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement
3. Terminology
3.1 Definitions:
3.1.1 contact angle, n—the interior angle that a drop makes between the substrate and a tangent drawn at the intersection
between the drop and the substrate as shown in Fig. 1; this is the angle formed by a liquid at the three phase boundary where a
liquid, gas (air) and solid intersect.
3.1.2 dispersion component, n—the component of solid surface tension that is related to intermolecular attraction caused by
nonpolar dispersion forces.
3.1.3 polar component, n—the component of solid surface tension that is related to polar forces, such as hydrogen bonding and
ion-dipole forces.
3.1.4 solid surface tension, n—the surface tension of a solid surface; this parameter cannot be measured directly, but must be
determined by extrapolation of polymer melt or solution data to 100 % solids or by contact angles with liquids of known surface
tension.
3.1.5 surface energy, n—excess free energy of surface molecules compared to those of the bulk material; arises from unbalanced
molecular cohesive forces at a surface that cause the surface to contract and behave like a film or membrane (units are energy/unit
2
areas such as joules/cm ).
1
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 D01.23 on Physical Properties of Applied Paint Films.
Current edition approved Dec. 15, 2008July 1, 2013. Published January 2009August 2013. Originally approved in 2008. Last previous edition approved in 2008 as D7394
– 08. DOI: 10.1520/D7490-08.10.1520/D7490-13.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
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
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7490 − 13
A = contact angle
D = drop of liquid
P = specimen
T = tangent at specimen surface
FIG. 1 Measuring Angle of Contact
3.1.6 surface tension, n—the force necessary to break the surface of a film of a given length (units are force/length, such as
dynes/cmdyn/cm or newtons/m); the same numerically as surface energy, but different units.
4. Summary of Test Method
4.1 Contact angles of drops of distilled water and diiodomethane (methylene iodide) are measured on the surface of interest.
The two values are then substituted into two separate expressions of the Owens-Wendt-Kaelble
...