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Standard Practice for Estimating Critical Surface TensionsTranslate name
STANDARD published on 1.7.2022
Designation standards: ASTM D7541-11(2022)
Publication date standards: 1.7.2022
The number of pages: 3
Approximate weight : 9 g (0.02 lbs)
Country: American technical standard
Category: Technical standards ASTM
critical surface tension, dewetting, surface contamination, wettability, wetting,, ICS Number Code 25.220.01 (Surface treatment and coating in general)
|Significance and Use|
5.1Knowledge of the critical surface tension of substrates, primers and other coatings is useful for explaining or predicting wettability by paints and other coatings applied to those surfaces. Surfaces with low critical surface tensions usually are prone to suffer defects such as crawling, picture framing, cratering and loss of adhesion when painted. Low or irregular values, or both, often are indicative of contamination that could reduce adhesion. Surfaces with high critical surface tensions are easy to wet and usually provide an excellent platform for painting.
5.2The swab, marking pen and draw-down tests all simulate the application of a film
5.3The swab and marking pen techniques are simple and rapid and are particularly useful for testing in the field or on curved, irregular or porous surfaces where contact angles cannot be measured. The drop test does not work well on such surfaces and the draw-down method requires a flat specimen that is relatively large.
5.4The estimation of critical surface tension has been useful in characterizing surfaces before and after cleaning processes such as power washes and solvent wipes in order to evaluate the efficiency of the cleaning.
5.5One or more of these techniques could be the basis of a go/no-go quality control test where if a certain liquid wets, the surface is acceptable for painting, but if that liquid retracts and crawls, the surface is not acceptable.
5.6Another go/no go test is possible where the test liquid is a paint and the surface is a substrate, primer or basecoat. A form of this test has been used for coatings for plastics.
1.1This practice covers procedures for estimating values of the critical surface tension of surfaces by observing the wetting and dewetting of a series of liquids (usually organic solvents) applied to the surface in question.
1.2Another technique, measurement of the contact angles, ?, of a series of test liquids and plotting cos ? versus surface tension (Zisman plots), provides data that allow the determination of more exact values for critical surface tension.
1.3The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4This 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.
1.5This 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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