ASTM_D_7490_-_13_2022.pdf

Designation:D749013(Reapproved 2022)Standard Test Method forMeasurement of the Surface Tension of Solid Coatings,Substrates and Pigments using Contact AngleMeasurements1This standard is issued under the fixed designation D7490;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method describes a procedure for the measure-ment of contact angles of two liquids,one polar and the othernonpolar,of known surface tension on a substrate,pigment(inthe form of a disk),or cured or air dried coating in order tocalculate the surface properties(surface tension and its disper-sion and polar components)of the solid.1.2 The total solid surface tension range that can be deter-mined using this method is approximately 20 to 60 dyn/cm.1.3 The values stated in CGS units(dyn/cm)are to beregarded as standard.No other units of measurement areincluded in this standard.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD5725 Test Method for Surface Wettability and Absorbencyof Sheeted Materials Using an Automated Contact AngleTester(Withdrawn 2010)3D7334 Practice for Surface Wettability of Coatings,Sub-strates and Pigments by Advancing Contact Angle Mea-surement3.Terminology3.1 Definitions:3.1.1 contact angle,nthe interior angle that a drop makesbetween the substrate and a tangent drawn at the intersectionbetween the drop and the substrate as shown in Fig.1;this isthe angle formed by a liquid at the three phase boundary wherea liquid,gas(air)and solid intersect.3.1.2 dispersion component,nthe component of solidsurface tension that is related to intermolecular attractioncaused by nonpolar dispersion forces.3.1.3 polar component,nthe component of solid surfacetension that is related to polar forces,such as hydrogenbonding and ion-dipole forces.3.1.4 solid surface tension,nthe surface tension of a solidsurface;this parameter cannot be measured directly,but mustbe determined by extrapolation of polymer melt or solutiondata to 100%solids or by contact angles with liquids of knownsurface tension.3.1.5 surface energy,nexcess free energy of surfacemolecules compared to those of the bulk material;arises fromunbalanced molecular cohesive forces at a surface that causethe surface to contract and behave like a film or membrane(units are energy/unit areas such as joules/cm2).3.1.6 surface tension,nthe force necessary to break thesurface of a film of a given length(units are force/length,suchas dyn/cm or newtons/m);the same numerically as surfaceenergy,but different units.4.Summary of Test Method4.1 Contact angles of drops of distilled water and di-iodomethane(methylene iodide)are measured on the surfaceof interest.The two values are then substituted into two1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings,Materials,and Applications and is the direct responsibility ofSubcommittee D01.23 on Physical Properties of Applied Paint Films.Current edition approved Jan.1,2022.Published January 2022.Originallyapproved in 2008.Last previous edition approved in 2013 as D7490 13.DOI:10.1520/D7490-13R22.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1separate expressions of the Owens-Wendt-Kaelble equation(one for each liquid).This results in two equations in twounknowns,which are then solved for the dispersion and polarcomponents of surface tension.The sum of the components isthe surface tension of the solid.5.Significance and Use5.1 The method d