ASTM D2805-11(2018) Standard Test Method for Hiding Power of Paints by Reflectometry.pdf

1、Designation: D2805 11 (Reapproved 2018)Standard Test Method forHiding Power of Paints by Reflectometry1This standard is issued under the fixed designation D2805; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi

2、sion. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.INTRODUCTIONUsing equations derived from Kubelka-Munk

3、 turbid media theory (1-4)2(see Annex A1), thereflectance of a coating can be predicted for any film thickness from measurements made at only one.On this basis several rapid and accurate test methods (5, 6) have been developed for determininghiding power. In the past such test methods have been cons

4、idered difficult due to complexities,apparent and actual, in the treatment of data. The present test method has been simplified in thisrespect, primarily by adapting it fully for computer calculations.Although the use of broad-band reflectometry makes this test method theoretically valid only fornon

5、chromatic (white or gray) colors, good agreement has been obtained with chromatic paints as well.This is undoubtedly because the experimental measurements are made fairly close to the hiding powerend point so that the Kubelka-Munk extrapolation and thus any associated error is relatively small.This

6、test method is therefore recommended without restriction as to color.1. Scope1.1 This test method covers the determination, withoutreference to a material paint standard, of the hiding power ofair dry coatings with Y tristimulus values greater than 15 %.With appropriate modification, it can also be

7、used to testbaking finishes.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of thi

8、s standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Deci

9、sion 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:3D344 Test Method for Relative Hiding Power of Paints bythe Visual Evaluation of B

10、rushoutsD1475 Test Method for Density of Liquid Coatings, Inks,and Related ProductsD3924 Specification for Standard Environment for Condi-tioning and Testing Paint, Varnish, Lacquer, and RelatedMaterials (Withdrawn 2016)4E284 Terminology of AppearanceE1247 Practice for Detecting Fluorescence in Obje

11、ct-ColorSpecimens by SpectrophotometryE1331 Test Method for Reflectance Factor and Color bySpectrophotometry Using Hemispherical GeometryE1347 Test Method for Color and Color-Difference Mea-surement by Tristimulus ColorimetryE1349 Test Method for Reflectance Factor and Color bySpectrophotometry Usin

12、g Bidirectional (45:0 or 0:45)Geometry3. Terminology3.1 DefinitionsFor definitions used in this test method, seeTerminology E284.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee

13、 D01.26 on Optical Properties.Current edition approved Feb. 1, 2018. Published February 2018. Originallyapproved in 1969. Last previous edition approved in 2011 as D2805 11. DOI:10.1520/D2805-11R18.2The boldface numbers in parentheses refer to the list of references at the end ofthis standard.3For r

14、eferenced 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.4The last approved version of this historical standard is reference

15、d 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 theDev

16、elopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2 Definitions of Terms Specific to This Standard:3.2.1 contrast ratio, nthe ratio of the reflectance of a filmon a black substrate to that of an ident

17、ical film on a whitesubstrate.3.2.1.1 CW,nthe contrast ratio with a white substrate ofreflectance W.Thus:CW5 R0/RW3.2.1.2 C, nthe contrast ratio with a white substrate forwhich W = 0.80.Thus:C 5 R0/R0.803.2.2 reflectance, nthe daylight luminous diffuse reflec-tance factor (specular reflection exclud

18、ed). Also referred to inthis test method as the Y-tristimulus value. This value may beexpressed as a percent or a decimal fraction, the latter beingpreferred and usually required for mathematical calculations.3.2.2.1 reflectivity, R,nthe reflectance of film thickenough to have the same reflectance o

19、ver both a black and awhite substrate.3.2.2.2 R0,nthe reflectance of a film on a black surfacewith a reflectance of 1 % or less, which is effectively zero forthe purpose of this test.3.2.2.3 W, nthe reflectance of a white substrate.3.2.2.4 RW,nthe reflectance of a film applied on a whitesubstrate of

20、 reflectance W.3.2.2.5 R0.80,nthe reflectance of a film applied on asubstrate having a reflectance of 80 %, which is the standardwhite-substrate reflectance in paint technology.3.2.3 scattering coeffcient, S, nthe ability of a material tointernally scatter and thereby reflect light; expressed in thi

21、s testmethod in the same units as spreading rate.3.2.4 spreading rate, H, nfilm area per unit volume ofcoating, in this test method expressed in square metres per litre(m2/L).3.2.4.1 spreading rate, HX,nan experimentally deter-mined value of H.3.2.4.2 spreading rate, HC,nvalue of H at a specifiedcon

22、trast ratio C.3.2.4.3 hiding power, H0.98,nthe spreading rate at thecontrast ratio C = 0.98.NOTE 1It should be emphasized that a contrast ratio of 0.98 does notrepresent visually complete hiding, nor does it indicate that the samecontrast ratio holds at every wavelength.4. Summary of Test Method4.1

23、The reflectivity Rof the coating is determined fromreflectance measurements on black and white hiding powercharts.4.2 The scattering coefficient S of the coating is determinedfrom R, and the reflectance R0and spreading rate HXof a filmapplied on black glass.4.3 The hiding power, H0.98of the coating

24、is calculatedfrom the reflectivity Rand the scattering coefficient S.4.4 As an optional procedure the contrast ratio C at aspecified spreading rate HCis calculated from Rand S.5. Significance and Use5.1 This is a precise instrumental method giving resultshaving an absolute physical significance with

25、out reference to acomparison paint. It should be used when maximum precisionand minimum subjectivity are required, as in testing specifica-tion coatings or evaluating the hiding efficiency of pigments.5.2 Hiding power Test Method D344 is visual instead ofinstrumental, and gives results that are rela

26、tive to a materialstandard instead of absolute. It is less precise than Test MethodD2805 but more closely aligned with practical painting proce-dures.6. Apparatus and Materials6.1 Substrates:6.1.1 Black Glass Panels, minimum size 200 by 200 mm,and approximately 6-mm thick.6.1.2 Black and White Paper

27、 ChartsThe surface shall besmooth and level, and impervious to paint liquids. The blackarea shall have a maximum reflectance of 1 % and the whitearea a minimum reflectance of 78 %. The white area shall benon-fluorescent, as observed visually under ultra-violetillumination, or determined in accordanc

28、e with Practice E1247.6.2 Balance, accurate to 0.1 mg.6.3 Glass SlidesRound or square plates of thicknesssimilar to that used for microscope specimen slides, with aminimum area of 40 cm2.6.4 Reflectance-Measuring Instrument5One that allowsonly diffusely reflected, radiant flux to be incident upon th

29、emeasuring element. It shall employ a photometric system,including source, filters, and receptor, that provides a responseclosely similar to the product of the spectral luminous effi-ciency function of the CIE standard observer and source C.Itshall provide readings to at least the third decimal plac

30、e andpermit estimation to the fourth.6.5 Template,6with a film area approximately 100 cm2determined to the nearest tenth. Record the exact value on LineC of the worksheet shown in Fig. 1.6.6 Doctor Blade Film Applicators, width 150 mm, clear-ances 50, 75, 100, 125, 150, 175, and 200 m.6.7 Computer a

31、nd Software, for solving the relevantKubelka-Munk equations.7. Procedure7.1 General Instructions:5Conforming with Test Methods E1331, E1347,orE1349. Other methods formeasuring the CIE-Y tristimulus value (specular reflection excluded) are permis-sible.6The sole source of supply of the template known

32、 to the committee at this timeis Paul Gardner Co., 316 N. E. First St., Pompano Beach, FL33061. If you are awareof alternative suppliers, please provide this information to ASTM InternationalHeadquarters. Your comments will receive careful consideration at a meeting of theresponsible technical commi

33、ttee,1which you may attend.D2805 11 (2018)27.1.1 Film ApplicationMake drawdowns manually with asmooth uniform motion, at the rate of about 6 cm/s. Hold papercharts flat by a vacuum plate or other suitable device whilemaking drawdowns.7.1.2 Reflectance MeasurementsMeasure the reflectanceof each test

34、area at a minimum of three locations, reading orestimating to four decimal places and calculating mean valuesto the same. Place charts over a white surface and black glassover a black surface while measurements are being made.7.1.3 Record KeepingRecord all data on a copy of theworksheet form specifi

35、ed in Fig. 1. Typical data entries areshown in Fig. 2.7.1.4 Weight MeasurementsMake all weighings to 0.1 mgon the analytical balance.7.2 Paint density, DDetermine the density in g/mL to fourdecimal places in accordance with Test Method D1475 andrecord on Line A of the worksheet (Fig. 1).7.3 Nonvolat

36、ile Content, NSandwich 0.3 mL of paint(dispensed with a 1-mL syringe) between two previouslyweighed slides, squeezing them together so that the paintspreads to a diameter of about 45 mm. Reweigh to obtain theweight of paint sample. Separate the slides, allow the films todry, and weigh a third time t

37、o determine the dry weight. Thencalculate the nonvolatile content of the paint as a decimalfraction to four places. Run in duplicate and report the meanvalue to three decimal places on Line B of the worksheet (Fig.1).7.4 Applicator SelectionMake trial drawdowns on blackand white charts at clearances

38、 of 100, 150, and 200 m. Allowthem to dry overnight and measure their contrast ratios. Basedon the results select the best applicator for a contrast ratio of0.97 6 0.01, which may be one of the trial applicators or oneof intermediate clearance. If it seems necessary, make anadditional trial drawdown

39、 to confirm the correct applicator.FIG. 1 Work Sheet FormD2805 11 (2018)37.5 Drawdowns on Glass and ChartsUsing the applicatorselected from 7.4, make four drawdowns each on black glassand on black and white charts in accordance with 7.1.1. Leaveenough of the white area of each chart uncoated to perm

40、itmeasurement of the reflectance W.7.6 Drying of the FilmsImmediately after applicationplace each drawdown horizontally in a well-ventilated dust-free location, with all drawdowns in close proximity to oneanother to assure identical drying conditions, and allow to drya minimum of 40 h before testing

41、. Drying conditions for filmapplications and nonvolatile determinations shall be the same,and in accordance with Specification D3924.7.7 Reflectance MeasurementsOn the second or third dayafter application measure the reflectances on all of the draw-downs within as brief a time span as possible, alte

42、rnating themeasurements between charts and glass rather than doing firstall one and then the other. Enter the values of R0, RW, and W forcharts into Section D of the worksheet, and the values of R0forglass into Section E.7.8 Weight of Dry Film, MAfter all of the reflectances aremeasured, position th

43、e template on the glass panels, each in itsturn, and scrape off the surplus paint with a razor blade, toleave film areas defined by the template. If the template area isnot already specified, measure one of the resultant filmscarefully to determine its area in square centimeters to thenearest tenth.

44、 Record this value on Line C of the worksheet(Fig. 1) as the characteristic area of the template. Then scrapeoff each paint film carefully into a weighing dish, weigh to 0.1mg, and record the weights M in Section E of the worksheet,entering each weight adjacent to the value of R0for the sameglass pa

45、nel.FIG. 2 Typical Work SheetD2805 11 (2018)48. Calculation8.1 In general, make the calculations and record to foursignificant figures and final report values to three. Entercalculated results in the worksheet (Fig. 1). Typical entries areshown in Fig. 2.8.2 Contrast Ratio CWand Reflectivity RFrom t

46、he dataentered in Section D of the worksheet calculate CWand Rforeach of the four charts, thus:CW5 R0/RW(1)R5 fR0, RW, W!Enter the values, as they are calculated, in the appropriatecolumns of Section D, then calculate and likewise enter theirmeans.8.3 Spreading Rate HXFrom the data recorded in thewo

47、rksheet on Lines A, B, and C and in Section E, calculate thespreading rate Hxfor each of the four glass panels, thus:HX5A 3N 3D10Mwhere:HX= spreading rate, m2/L,A = template area, cm2,N = nonvolatile content of the paint,D = density of the paint, g/mL, andM = dry film weight, g.and enter the values

48、in the appropriate column of Section E.8.4 Scattering Coeffcient S and Hiding Power H0.98Continuing on Section E of the worksheet (see Fig. 1), andusing the mean value of Rfrom Section D, calculate for eachof the glass panels, first S and then H0.98in square millimetresper litre as follows:S 5 fR0,

49、R, HX! (2)H0.985 fS, C, R! given C 5 0.98 (3)Enter the values as they are calculated in the appropriatecolumns of Section E, then calculate and likewise enter theirmeans.8.5 Contrast Ratio C at a Specified Spreading Rate HIfdesired, calculate the contrast ratio at a specified spreading rateusing the mean values of Rand S from worktable Sections Dand E, of the worksheet (Fig. 1), thus:C 5 fS, H, R! (4)9. Report9.1 Enter the following information on the indicated line inFig. 1, Section G:9.1.1 Hiding Po