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Standard Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle MeasurementPřeložit název
NORMA vydána dne 1.1.2022
Označení normy: ASTM D7334-08(2022)
Datum vydání normy: 1.1.2022
Kód zboží: NS-1048067
Počet stran: 3
Přibližná hmotnost: 9 g (0.02 liber)
Země: Americká technická norma
Kategorie: Technické normy ASTM
advancing contact angles, contact angles, surface tensions, wettability, wettings,, ICS Number Code 87.040 (Paints and varnishes)
|Significance and Use|
5.1This 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.
5.2This 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.
5.3Although 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.
5.4A low advancing contact angle value (<45) is indicative of wetting and angles of 10 to 20 are indicative of excellent wetting.
5.5Water can be used as a test liquid to establish (via the advancing contact angle) whether a surface is hydrophilic (angle <45), hydrophobic (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.
5.6An 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.
5.7In 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.
5.8Contact 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 infrared microscopy would be needed to identify the chemical moieties that give the contact angle differences.
5.9This test method can be used on nearly all coatings and substrates and may be extended to pigments by compressing the pigment powder into a solid disk.
1.1This 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.
1.2There are two types of contact angles, advancing and receding. This standard deals only with advancing contact angles.
1.3This practice is intended to supplement the manufacturers instructions for the device being used to make the measurements, but is not intended to replace them.
1.4A common test liquid is water, but many other liquids such as solvents, surfactant and dispersant solutions and even liquid paints can be used.
1.5This practice is based on goniometry, which involves the observation of a sessile drop of test liquid on a solid substrate.
1.6Although contact angles are governed by surface tension, this standard cannot be used to measure surface tension directly.
1.7The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.
1.8This 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.
1.9This 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|
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