ASTM D7334-08(2022)

Standard Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement

SIGNIFICANCE AND USE
5.1 This standard is useful for characterizing the wettability of surfaces. A surface that is easy to wet is one over which a coating is more likely to give good adhesion and appearance and less likely to suffer surface tension related defects such as crawling, cratering, pinholing and orange peel.  
5.2 This standard also can be used to test pigment surfaces for wettability, particularly by potential surfactant- or resin-based dispersants or mill bases. Easily wetted pigments are more likely to be easy to disperse and dispersants/mill bases that wet pigments of interest are more likely to disperse those pigments well.  
5.3 Although the contact angle is governed by the surface tensions of the test liquid and test surface, the angle cannot provide a surface tension value directly.  
5.4 A low advancing contact angle value (  
5.5 Water can be used as a test liquid to establish (via the advancing contact angle) whether a surface is hydrophilic (angle 90°) or somewhere in-between (angle of 45 to 90°). Water contact angles have been used to estimate surface cleanliness before and after cleaning operations, ease of wettability of surfaces by waterborne coatings and the effectiveness of rinsing processes.  
5.6 An organic liquid such as a solvent also can be used to characterize a substrate, coating or pigment. The resultant contact angle will depend on the surface tensions of the liquid and the test surface. A low surface tension (energy) test surface will not be wet by a high surface tension liquid.  
5.7 In addition to water and solvents, a surfactant dispersion or dispersant solution can be used to test a pigment surface. Any test liquid that is a potential dispersant for a test pigment must wet the pigment well or it will not work as a dispersant.  
5.8 Contact angle measurements can be used to map surfaces in terms of hydrophilicity, presence of low surface tension components or contaminants, or variations in composition. Other analytical methods such as inf...
SCOPE
1.1 This practice covers the measurement of the angle of contact when a drop of liquid is applied to a coated surface, substrate, or preformed disk of pigment.  
1.2 There are two types of contact angles, advancing and receding. This standard deals only with advancing contact angles.  
1.3 This practice is intended to supplement the manufacturer’s instructions for the device being used to make the measurements, but is not intended to replace them.  
1.4 A common test liquid is water, but many other liquids such as solvents, surfactant and dispersant solutions and even liquid paints can be used.  
1.5 This practice is based on goniometry, which involves the observation of a sessile drop of test liquid on a solid substrate.  
1.6 Although contact angles are governed by surface tension, this standard cannot be used to measure surface tension directly.  
1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.  
1.8 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.  
1.9 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: 31-Dec-2021
• 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)

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: D7334 − 08 (Reapproved 2022)
Standard Practice for
Surface Wettability of Coatings, Substrates and Pigments
1
by Advancing Contact Angle Measurement
This standard is issued under the fixed designation D7334; 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 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This practice covers the measurement of the angle of
D1193 Specification for Reagent Water
contact when a drop of liquid is applied to a coated surface,
D5725 Test Method for Surface Wettability andAbsorbency
substrate, or preformed disk of pigment.
of Sheeted Materials Using an Automated Contact Angle
1.2 There are two types of contact angles, advancing and
3
Tester (Withdrawn 2010)
receding. This standard deals only with advancing contact
angles.
3. Terminology
1.3 This practice is intended to supplement the manufactur-
3.1 Definitions:
er’s instructions for the device being used to make the
3.1.1 advancing contact angle, n—the contact angle that is
measurements, but is not intended to replace them.
measured immediately after the sessile drop is placed on the
surface.
1.4 A common test liquid is water, but many other liquids
3.1.1.1 Discussion—The drop has the maximum volume
such as solvents, surfactant and dispersant solutions and even
allowable for the liquid-solid interfacial area: any addition will
liquid paints can be used.
make the drop expand and increase the liquid-solid interfacial
1.5 Thispracticeisbasedongoniometry,whichinvolvesthe
area. This can be thought of as the “wetting angle” because the
observation of a sessile drop of test liquid on a solid substrate.
drop is ready to wet additional area. This is the contact angle
used in this method and in most coating measurements.
1.6 Although contact angles are governed by surface
tension, this standard cannot be used to measure surface 3.1.2 contact angle, n—the interior angle that a drop makes
tension directly. between the substrate and a tangent drawn at the intersection
between the drop and the substrate as shown in Fig. 1.
1.7 The values stated in SI units are to be regarded as the
3.1.2.1 Discussion—This is the angle formed by a liquid at
standard. The values given in parentheses are for information
the three phase boundary where a liquid, gas (air) and solid
only.
intersect.
1.8 This standard does not purport to address all of the
3.1.3 receding contact angle, n—thecontactanglemeasured
safety concerns, if any, associated with its use. It is the
when material is removed from the drop so that it contracts.
responsibility of the user of this standard to establish appro-
3.1.3.1 Discussion—The liquid-solid interfacial area will
priate safety, health, and environmental practices and deter-
decrease. This is the “de-wetting angle.”
mine the applicability of regulatory limitations prior to use.
3.1.4 sessile drop, n—drop of liquid on the upper side of a
1.9 This international standard was developed in accor-
horizontal surface (as in Fig. 1).
dance with internationally recognized principles on standard-
3.1.5 surface tension, n, and surface energy, n—the terms
ization established in the Decision on Principles for the
surface tension and surface energy are often used interchange-
Development of International Standards, Guides and Recom-
ably.
mendations issued by the World Trade Organization Technical
3.1.5.1 Discussion—They are the same numerically, al-
Barriers to Trade (TBT) Committee.
thoughtheyhavedifferentunits.Theyaremeasuresofaneffect
1 2
This practice is under the jurisdiction of ASTM Committee D01 on Paint and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Related Coatings, Materials, and Applications and is the direct responsibility of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Subcommittee D01.23 on Physical Properties of Applied Paint Films. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Jan. 1, 2022. Published January 2022. Originally the ASTM website.
3
approved in 2008. Last previous edition approved in 2013 as D7334 – 08 (2013). The last approved version of this historical standard is referenced on
DOI: 10.1520/D7334-08R22. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7334 − 08 (2022)
operations
...